Various Licenses and Comments about Them

Table of Contents

Introduction

We classify a license according to certain key criteria:

We try to list the most commonly encountered free software license on this page, but cannot list them all; we'll try our best to answer questions about free software licenses whether or not they are listed here. The licenses are more or less in alphabetical order within each section.

If you believe you have found a violation of one of our licenses, please refer to our license violation page.

If you want help choosing a license, evaluating a license, or have other questions about licenses, you can email us at <licensing@fsf.org>. We have a very large backlog of requests, so please read our web pages here first, you'll get an answer sooner. Also, the more specific your question is, the more likely we'll be able to answer it quickly. (We also welcome knowledgeable volunteers to help answer licensing questions.)

If you are contemplating writing a new license, please also contact us at <licensing@fsf.org>. The proliferation of different free software licenses is a significant problem in the free software community today, both for users and developers. We will do our best to help you find an existing free software license that meets your needs.

Software Licenses

GPL-Compatible Free Software Licenses

The following licenses qualify as free software licenses, and are compatible with the GNU GPL.

GNU General Public License (GPL) version 3

This is the latest version of the GNU GPL: a free software license, and a copyleft license. We recommend it for most software packages.

Please note that GPLv3 is not compatible with GPLv2 by itself. However, most software released under GPLv2 allows you to use the terms of later versions of the GPL as well. When this is the case, you can use the code under GPLv3 to make the desired combination. To learn more about compatibility between GNU licenses, please see our FAQ.

GNU General Public License (GPL) version 2

This is the previous version of the GNU GPL: a free software license, and a copyleft license. We recommend the latest version for most software.

Please note that GPLv2 is, by itself, not compatible with GPLv3. However, most software released under GPLv2 allows you to use the terms of later versions of the GPL as well. When this is the case, you can use the code under GPLv3 to make the desired combination. To learn more about compatibility between GNU licenses, please see our FAQ.

GNU Lesser General Public License (LGPL) version 3

This is the latest version of the LGPL: a free software license, but not a strong copyleft license, because it permits linking with non-free modules. It is compatible with GPLv3. We recommend it for special circumstances only.

Please note that LGPLv3 is not compatible with GPLv2 by itself. However, most software released under GPLv2 allows you to use the terms of later versions of the GPL as well. When this is the case, you can use the code under GPLv3 to make the desired combination. To learn more about compatibility between GNU licenses, please see our FAQ.

GNU Lesser General Public License (LGPL) version 2.1

This is the previous version of the LGPL: a free software license, but not a strong copyleft license, because it permits linking with non-free modules. It is compatible with GPLv2 and GPLv3. We generally recommend the latest version of the LGPL, for special circumstances only. To learn more about how LGPLv2.1 is compatible with other GNU licenses, please see our FAQ.

GNU Affero General Public License (AGPL) version 3

This is a free software, copyleft license. Its terms effectively consist of the terms of GPLv3, with an additional paragraph in section 13 to allow users who interact with the licensed software over a network to receive the source for that program. We recommend that developers consider using the GNU AGPL for any software which will commonly be run over a network.

Please note that the GNU AGPL is not compatible with GPLv2. It is also technically not compatible with GPLv3 in a strict sense: you cannot take code released under the GNU AGPL and convey or modify it however you like under the terms of GPLv3, or vice versa. However, you are allowed to combine separate modules or source files released under both of those licenses in a single project, which will provide many programmers with all the permission they need to make the programs they want. See section 13 of both licenses for details.

GNU All-Permissive License

This is a simple permissive free software license, compatible with the GNU GPL, which we recommend GNU packages use for README and other small supporting files. All developers can feel free to use it in similar situations.

Older versions of this license did not have the second sentence with the express warranty disclaimer. This same analysis applies to both versions.

Apache License, Version 2.0

This is a free software license, compatible with version 3 of the GPL.

Please note that this license is not compatible with GPL version 2, because it has some requirements that are not in the older version. These include certain patent termination and indemnification provisions.

Artistic License 2.0

This license is a free software license, compatible with the GPL thanks to the relicensing option in section 4(c)(ii).

Berkeley Database License (aka the Sleepycat Software Product License)

This is a free software license, compatible with the GNU GPL.

Boost Software License

This is a simple, permissive non-copyleft free software license, compatible with the GNU GPL.

Modified BSD license

(Note: on the preceding link, the modified BSD license is listed in the General section.)

This is the original BSD license, modified by removal of the advertising clause. It is a simple, permissive non-copyleft free software license, compatible with the GNU GPL.

If you want a simple, permissive non-copyleft free software license, the modified BSD license is a reasonable choice. However, it is risky to recommend use of “the BSD license”, because confusion could easily occur and lead to use of the flawed original BSD license. To avoid this risk, you can suggest the X11 license instead. The X11 license and the revised BSD license are more or less equivalent.

This license is sometimes referred to as the 3-clause BSD license.

CeCILL version 2

The CeCILL is a free software license, explicitly compatible with the GNU GPL.

The text of the CeCILL uses a couple of biased terms that ought to be avoided: “intellectual property” (see this article) and “protection” (see this article); this decision was unfortunate, because reading the license tends to spread the presuppositions of those terms. However, this does not cause any particular problem for the programs released under the CeCILL.

Section 9.4 of the CeCILL commits the program's developers to certain forms of cooperation with the users, if someone attacks the program with a patent. You might look at that as a problem for the developer; however, if you are sure you would want to cooperate with the users in those ways anyway, then it isn't a problem for you.

The Clear BSD License

This is a free software license, compatible with both GPLv2 and GPLv3. It is based on the modified BSD license, and adds a term expressly stating it does not grant you any patent licenses. Because of this, we encourage you to be careful about using software under this license; you should first consider whether the licensor might want to sue you for patent infringement. If the developer is disclaiming patent licenses to set up a trap for you, it would be wise to avoid the program.

Cryptix General License

This is a simple, permissive non-copyleft free software license, compatible with the GNU GPL. It is very similar to the X11 license.

eCos license version 2.0

The eCos license version 2.0 is a GPL-compatible free software license. It consists of the GPL, plus an exception allowing linking to software not under the GPL. This license has the same disadvantages as the LGPL.

Educational Community License 2.0

This is a free software license, and it is compatible with GPLv3. It is based on the Apache License 2.0; the scope of the patent license has changed so that when an organization's employee works on a project, the organization does not have to license all of its patents to recipients. This patent license and the indemnification clause in section 9 make this license incompatible with GPLv2.

Eiffel Forum License, version 2

This is a free software license, compatible with the GNU GPL. Previous releases of the Eiffel license are not compatible with the GPL.

EU DataGrid Software License

This is a simple, permissive non-copyleft free software license, compatible with the GNU GPL.

Expat License

This is a simple, permissive non-copyleft free software license, compatible with the GNU GPL. It is sometimes ambiguously referred to as the MIT License.

FreeBSD license

This is the original BSD license with the advertising clause and another clause removed. (It is also sometimes called the “2-clause BSD license”.) It is a simple, permissive non-copyleft free software license, compatible with the GNU GPL.

If you want a simple, permissive non-copyleft free software license, the FreeBSD license is a reasonable choice. However, please don't call it a “BSD” or “BSD-style” license, because that is likely to cause confusion which could lead to use of the flawed original BSD license.

Freetype Project License

This is a free software license, and compatible with GPLv3. It has some attribution requirements which make it incompatible with GPLv2.

License of the iMatix Standard Function Library

This is a free software license and is GPL compatible.

Independent JPEG Group License

This is a free software license, and compatible with the GNU GPL. The authors have assured us that developers who document changes as required by the GPL will also comply with the similar requirement in this license.

License of imlib2

This is a free software license, and GPL-compatible. The author has explained to us that the GPL's options for providing source all mean the source has been "made available publicly" in their words.

Intel Open Source License

This is a Free Software license, compatible with the GNU GPL.

ISC License

This license is sometimes also known as the OpenBSD License. It is a free software license, and compatible with the GNU GPL.

This license does have an unfortunate wording choice: it provides recipients with "Permission to use, copy, modify, and/or distribute this software...." This is roughly the same language from the license of Pine that the University of Washington later claimed prohibited people from distributing modified versions of the software.

ISC has told us they do not share the University of Washington's interpretation, and we have every reason to believe them. Thus, there's no reason to avoid software released under this license. However, to help make sure this language cannot cause any trouble in the future, we encourage developers to choose a different license for their own works. The Expat License and FreeBSD License is similarly permissive and brief.

NCSA/University of Illinois Open Source License

This license is based on the terms of the Expat and modified BSD licenses. It is a simple, permissive non-copyleft free software license, compatible with the GNU GPL.

License of Netscape Javascript

This is the disjunction of the Netscape Public License and the GNU GPL. Because of that, it is a free software license, compatible with the GNU GPL, but not a strong copyleft.

This disjunctive license is a good choice if you want to make your package GPL-compatible and MPL-compatible. However, you can also accomplish that by using the LGPL or the Guile license.

Such a disjunctive license might be a good choice if you have been using the MPL, and want to change to a GPL-compatible license without subtracting any permission you have given for previous versions.

OpenLDAP License, Version 2.7

This is a permissive non-copyleft free software license that is compatible with the GNU GPL.

License of Perl 5 and below

This license is the disjunction of the Artistic License 1.0 and the GNU GPL—in other words, you can choose either of those two licenses. It qualifies as a free software license, but it may not be a real copyleft. It is compatible with the GNU GPL because the GNU GPL is one of the alternatives.

We recommend you use this license for any Perl 4 or Perl 5 package you write, to promote coherence and uniformity in Perl programming. Outside of Perl, we urge you not to use this license; it is better to use just the GNU GPL.

Public Domain

Being in the public domain is not a license; rather, it means the material is not copyrighted and no license is needed. Practically speaking, though, if a work is in the public domain, it might as well have an all-permissive non-copyleft free software license. Public domain material is compatible with the GNU GPL.

License of Python 2.0.1, 2.1.1, and newer versions

This is a free software license and is compatible with the GNU GPL. Please note, however, that intermediate versions of Python (1.6b1, through 2.0 and 2.1) are under a different license (see below).

License of Python 1.6a2 and earlier versions

This is a free software license and is compatible with the GNU GPL. Please note, however, that newer versions of Python are under other licenses (see above and below).

License of Ruby

This is a free software license, compatible with the GPL via an explicit dual-licensing clause.

SGI Free Software License B, version 2.0

The SGI Free Software License B version 2.0 is a free software license. It is essentially identical to the X11 License, with an optional alternative way of providing license notices.

Previous versions of the SGI Free Software License B were not free software licenses, despite their name. However, they all included clauses that allow you to upgrade to new versions of the license, if you choose to do so. As a result, if a piece of software was released under any version of the SGI Free License B, you can use it under the terms of this free version.

Standard ML of New Jersey Copyright License

This is a simple, permissive non-copyleft free software license, compatible with the GNU GPL.

Unicode, Inc. License Agreement for Data Files and Software

This is a license that Unicode, Inc. has applied to the Unicode Character Database—various data files that developers can use to help implement the Unicode standard in their own programs. It is a simple permissive license, compatible with all versions of the GPL.

If you want to use files covered by this License Agreement in your own software, that shouldn't be any problem, but we recommend that you also include a full copy of its text. Some of the files contain alternative license terms which are nonfree, or no licensing information at all, so including a copy of the License Agreement will help avoid confusion when others want to distribute your software. Of course, you'll also need to follow the conditions in this License Agreement for distributing the files, but those are very straightforward.

Please take care to ensure that the files you are using are covered by this License Agreement. Other files published by Unicode, Inc. are covered by the Unicode Terms of Use, a different, nonfree license that appears on the same page but covers different files. A short explanation at the top of this License Agreement details which files it covers.

Please do not use this License Agreement for your own software. If you want to use a simple permissive license for your project, please use the Expat license; it is by far more common, and widely recognized in the free software community.

License of Vim, Version 6.1 or later

This is a free software license, partially copyleft but not really. It is compatible with the GPL, by an explicit conversion clause.

W3C Software Notice and License

This is a free software license and is GPL compatible.

WTFPL, Version 2

This is a free software license, very permissive and GPL-compatible.

X11 License

This is a simple, permissive non-copyleft free software license, compatible with the GNU GPL. Older versions of XFree86 used the same license, and some of the current variants of XFree86 also do. Later versions of XFree86 are distributed under the XFree86 1.1 license.

This license is sometimes called the MIT license, but that term is misleading, since MIT has used many licenses for software.

XFree86 1.1 License

This is a simple, permissive non-copyleft free software license, compatible with version 3 of the GPL.

Please note that this license is incompatible with version 2 of the GPL, because of its requirements that apply to all documentation in the distribution that contain acknowledgements.

There are currently several variants of XFree86, and only some of them use this license. Some continue to use the X11 license.

License of ZLib

This is a free software license, and compatible with the GPL.

Zope Public License, versions 2.0 and 2.1

This is a simple, permissive non-copyleft free software license which is compatible with the GNU GPL.

GPL-Incompatible Free Software Licenses

The following licenses are free software licenses, but are not compatible with the GNU GPL.

Affero General Public License version 1

The Affero General Public License is a free software license, copyleft, and incompatible with the GNU GPL. It consists of the GNU GPL version 2, with one additional section that Affero added with FSF approval. The new section, 2(d), covers the distribution of application programs through web services or computer networks.

This license has been succeeded by the GNU Affero General Public License version 3; please use that instead.

Academic Free License, all versions through 3.0

The Academic Free License is a free software license, not copyleft, and incompatible with the GNU GPL. Recent versions contain contract clauses similar to the Open Software License, and should be avoided for the same reasons.

Apache License, Version 1.1

This is a permissive non-copyleft free software license. It has a few requirements that render it incompatible with the GNU GPL, such as strong prohibitions on the use of Apache-related names.

Apache License, Version 1.0

This is a simple, permissive non-copyleft free software license with an advertising clause. This creates practical problems like those of the original BSD license, including incompatibility with the GNU GPL.

Apple Public Source License (APSL), version 2

This is a free software license, incompatible with the GNU GPL. We recommend that you not use this license for new software that you write, but it is ok to use and improve the software released under this license. More explanation.

BitTorrent Open Source License

This is a free software license, but incompatible with the GPL, for the same reasons as the Jabber Open Source License.

Original BSD license

(Note: on the preceding link, the original BSD license is listed in the UCB/LBL section. This license is also sometimes called the “4-clause BSD license”.)

This is a simple, permissive non-copyleft free software license with a serious flaw: the “obnoxious BSD advertising clause”. The flaw is not fatal; that is, it does not render the software non-free. But it does cause practical problems, including incompatibility with the GNU GPL.

We urge you not to use the original BSD license for software you write. If you want to use a simple, permissive non-copyleft free software license, it is much better to use the modified BSD license or the X11 license. However, there is no reason not to use programs that have been released under the original BSD license.

Common Development and Distribution License (CDDL), version 1.0

This is a free software license. It has a copyleft with a scope that's similar to the one in the Mozilla Public License, which makes it incompatible with the GNU GPL. This means a module covered by the GPL and a module covered by the CDDL cannot legally be linked together. We urge you not to use the CDDL for this reason.

Also unfortunate in the CDDL is its use of the term “intellectual property”.

Common Public Attribution License 1.0 (CPAL)

This is a free software license. It is based on the Mozilla Public License, and is incompatible with the GPL for the same reasons: it has several requirements for modified versions that do not exist in the GPL. It also requires you to publish the source of the program if you allow others to use it.

Common Public License Version 1.0

This is a free software license. Unfortunately, its weak copyleft and choice of law clause make it incompatible with the GNU GPL.

Condor Public License

This is a free software license. It has a couple of requirements that make it incompatible with the GNU GPL, including strong restrictions on the use of Condor-related names, and a condition that you must comply with United States export laws.

Eclipse Public License Version 1.0

The Eclipse Public License is similar to the Common Public License, and our comments on the CPL apply equally to the EPL. The only change is that the EPL removes the broader patent retaliation language regarding patent infringement suits specifically against Contributors to the EPL'd program.

European Union Public License (EUPL) version 1.1

This is a free software license. By itself, it has a copyleft comparable to the GPL's. However, it allows recipients to distribute the work under the terms of other selected licenses, and some of those—the Mozilla Public License and the Common Public License in particular—only provide a weaker copyleft. Thus, developers can't rely on this license to provide a strong copyleft.

The EUPL is compatible with GPLv2, because that is listed as one of the alternative licenses that recipients may use. However, it is incompatible with GPLv3, because recipients are not given permission to use GPLv3's terms, and the EUPL's copyleft conflicts with GPLv3's. Because of this incompatibility, we urge you not to use the EUPL for any software you write.

IBM Public License, Version 1.0

This is a free software license. Unfortunately, it has a choice of law clause which makes it incompatible with the GNU GPL.

Interbase Public License, Version 1.0

This is a free software license that is essentially the same as the Mozilla Public License, Version 1.1. Like the MPL, the IPL has some complex restrictions that make it incompatible with the GNU GPL. That is, a module covered by the GPL and a module covered by the IPL cannot legally be linked together. We urge you not to use the IPL for this reason.

Jabber Open Source License, Version 1.0

The license is a free software license, incompatible with the GPL. It permits relicensing under a certain class of licenses, those which include all the requirements of the Jabber license. The GPL is not a member of that class, so the Jabber license does not permit relicensing under the GPL. Therefore, it is not compatible.

LaTeX Project Public License 1.3a

We have not written a full analysis of this license, but it is a free software license, with less stringent requirements on distribution than LPPL 1.2 (described next). It is still incompatible with the GPL because some modified versions must include a copy of or pointer to an unmodified version.

LaTeX Project Public License 1.2

This license is an incomplete statement of the distribution terms for LaTeX. As far as it goes, it is a free software license, but incompatible with the GPL because it has many requirements that are not in the GPL.

This license contains complex and annoying restrictions on how to publish a modified version, including one requirement that falls just barely on the good side of the line of what is acceptable: that any modified file must have a new name.

The reason this requirement is acceptable for LaTeX is that TeX has a facility to allow you to map file names, to specify “use file bar when file foo is requested”. With this facility, the requirement is merely annoying; without the facility, the same requirement would be a serious obstacle, and we would have to conclude it makes the program non-free.

The LPPL says that some files, in certain versions of LaTeX, may have additional restrictions, which could render them non-free. For this reason, it may take some careful checking to produce a version of LaTeX that is free software.

The LPPL makes the controversial claim that simply having files on a machine where a few other people could log in and access them in itself constitutes distribution. We believe courts would not uphold this claim, but it is not good for people to start making the claim.

Please do not use this license for any other project.

Note: These comments are for version 1.2 (3 Sep 1999) of the LPPL.

Lucent Public License Version 1.02 (Plan 9 license)

This is a free software license, but it is incompatible with the GNU GPL because of its choice of law clause. We recommend that you not use this license for new software that you write, but it is ok to use and improve Plan 9 under this license.

Microsoft Public License (Ms-PL)

This is a free software license; it has a copyleft that is not strong, but incompatible with the GNU GPL. We urge you not to use the Ms-PL for this reason.

Microsoft Reciprocal License (Ms-RL)

This is a free software license. It's based on the Microsoft Public License, and has an additional clause to make the copyleft just a little bit stronger. It's also incompatible with the GNU GPL, and we urge you not to use the Ms-RL for this reason.

Mozilla Public License (MPL)

This is a free software license which is not a strong copyleft; unlike the X11 license, it has some complex restrictions that make it incompatible with the GNU GPL. That is, a module covered by the GPL and a module covered by the MPL cannot legally be linked together. We urge you not to use the MPL for this reason.

However, MPL 1.1 has a provision (section 13) that allows a program (or parts of it) to offer a choice of another license as well. If part of a program allows the GNU GPL as an alternate choice, or any other GPL-compatible license as an alternate choice, that part of the program has a GPL-compatible license.

Netizen Open Source License (NOSL), Version 1.0

This is a free software license that is essentially the same as the Mozilla Public License, Version 1.1. Like the MPL, the NOSL has some complex restrictions that make it incompatible with the GNU GPL. That is, a module covered by the GPL and a module covered by the NOSL cannot legally be linked together. We urge you not to use the NOSL for this reason.

Netscape Public License (NPL), versions 1.0 and 1.1

This is a free software license, not a strong copyleft, and incompatible with the GNU GPL. It consists of the Mozilla Public License with an added clause that permits Netscape to use your added code even in their proprietary versions of the program. Of course, they do not give you permission to use their code in the analogous way. We urge you not to use the NPL.

Nokia Open Source License

This is similar to the Mozilla Public License: a free software license incompatible with the GNU GPL.

Old OpenLDAP License, Version 2.3

This is a permissive non-copyleft free software license with a few requirements (in sections 4 and 5) that render it incompatible with the GNU GPL. Note that the latest version of OpenLDAP has a different license that is compatible with the GNU GPL.

We urge you not to use the older OpenLDAP license for software you write. However, there is no reason to avoid running programs that have been released under this license.

Open Software License, all versions through 3.0

The Open Software License is a free software license. It is incompatible with the GNU GPL in several ways.

Recent versions of the Open Software License have a term which requires distributors to try to obtain explicit assent to the license. This means that distributing OSL software on ordinary FTP sites, sending patches to ordinary mailing lists, or storing the software in an ordinary version control system, is arguably a violation of the license and would subject you to possible termination of the license. Thus, the Open Software License makes it very difficult to develop software using the ordinary tools of free software development. For this reason, and because it is incompatible with the GPL, we recommend that no version of the OSL be used for any software.

We urge you not to use the Open Software License for software you write. However, there is no reason to avoid running programs that have been released under this license.

OpenSSL license

The license of OpenSSL is a conjunction of two licenses, one of them being the license of SSLeay. You must follow both. The combination results in a copyleft free software license that is incompatible with the GNU GPL. It also has an advertising clause like the original BSD license and the Apache license.

We recommend using GNUTLS instead of OpenSSL in software you write. However, there is no reason not to use OpenSSL and applications that work with OpenSSL.

Phorum License, Version 2.0

This is a free software license but it is incompatible with the GPL. Section 5 makes the license incompatible with the GPL.

PHP License, Version 3.01

This license is used by most of PHP4. It is a non-copyleft free software license. It is incompatible with the GNU GPL because it includes strong restrictions on the use of “PHP” in the name of derived products.

We recommend that you not use this license for anything except PHP add-ons.

License of Python 1.6b1 through 2.0 and 2.1

This is a free software license but is incompatible with the GNU GPL. The primary incompatibility is that this Python license is governed by the laws of the State of Virginia, in the USA, and the GPL does not permit this.

Q Public License (QPL), Version 1.0

This is a non-copyleft free software license which is incompatible with the GNU GPL. It also causes major practical inconvenience, because modified sources can only be distributed as patches.

We recommend that you avoid using the QPL for anything that you write, and use QPL-covered software packages only when absolutely necessary. However, this avoidance no longer applies to Qt itself, since Qt is now also released under the GNU GPL.

Since the QPL is incompatible with the GNU GPL, you cannot take a GPL-covered program and QPL-covered program and link them together, no matter how.

However, if you have written a program that uses QPL-covered library (called FOO), and you want to release your program under the GNU GPL, you can easily do that. You can resolve the conflict for your program by adding a notice like this to it:

  As a special exception, you have permission to link this program
  with the FOO library and distribute executables, as long as you
  follow the requirements of the GNU GPL in regard to all of the
  software in the executable aside from FOO.

You can do this, legally, if you are the copyright holder for the program. Add it in the source files, after the notice that says the program is covered by the GNU GPL.

RealNetworks Public Source License (RPSL), Version 1.0

The RPSL is a free software license that is GPL-incompatible for a number of reasons: it requires that derivative works be licensed under the terms of the RPSL, and mandates that any litigation take place in Seattle, Washington.

Sun Industry Standards Source License 1.0

This is a free software license, not a strong copyleft, which is incompatible with the GNU GPL because of details rather than any major policy.

Sun Public License

This is essentially the same as the Mozilla Public License: a free software license incompatible with the GNU GPL. Please do not confuse this with the Sun Community Source License which is not a free software license.

License of xinetd

This is a copyleft free software license, incompatible with the GPL. It is incompatible because it places extra restrictions on redistribution of modified versions that contradict the redistribution requirements in the GPL.

Yahoo! Public License 1.0

This is a free software license. It has a copyleft similar to the one found in the Mozilla Public License. It also has a choice of law clause in section 7. These features both make the license GPL-incompatible. The license also unfortunately uses the term “intellectual property”.

Zend License, Version 2.0

This license is used by one part of PHP4. It is a non-copyleft free software license which is incompatible with the GNU GPL, and has practical problems like those of the original BSD license.

We recommend that you not use this license for anything you write.

Zope Public License version 1

This is a simple, fairly permissive non-copyleft free software license with practical problems like those of the original BSD license, including incompatibility with the GNU GPL.

We urge you not to use the ZPL version 1 for software you write. However, there is no reason to avoid running programs that have been released under this license, such as previous versions of Zope.

Version 2.0 of the Zope Public License is GPL-compatible.

Non-Free Software Licenses

The following licenses do not qualify as free software licenses. A non-free license is automatically incompatible with the GNU GPL.

Of course, we urge you to avoid using non-free software licenses, and to avoid non-free software in general.

There is no way we could list all the known non-free software licenses here; after all, every proprietary software company has its own. We focus here on licenses that are often mistaken for free software licenses but are, in fact, not free software licenses.

We have provided links to these licenses when we can do so without violating our general policy: that we do not make links to sites that promote, encourage or facilitate the use of non-free software packages. The last thing we want to do is give any non-free program some gratis publicity that might encourage more people to use it. For the same reason, we have avoided naming the programs for which a license is used, unless we think that for specific reasons it won't backfire.

Aladdin Free Public License

Despite its name, this is not a free software license because it does not allow charging for distribution, and largely prohibits simply packaging software licensed under it with anything for which a charge is made.

Apple Public Source License (APSL), version 1.x

Versions 1.0, 1.1 and 1.2 are not free software licenses (follow the link for more explanation). Please don't use these licenses, and we urge you to avoid any software that has been released under them. Version 2.0 of the APSL is a free software license.

Artistic License 1.0

We cannot say that this is a free software license because it is too vague; some passages are too clever for their own good, and their meaning is not clear. We urge you to avoid using it, except as part of the disjunctive license of Perl.

AT&T Public License

The AT&T Public License is a non-free license. It has several serious problems:

  1. The patent license is voided by any modification, no matter how small, of the pertinent code.
  2. You must demand a written agreement when you distribute the sources or patches.
  3. It requires notifying AT&T if you distribute a patch.
  4. Your license can be terminated through no fault of yours, under section 8/3.
  5. It makes compliance with export control laws a condition of the license.
  6. Some versions of the license require you to provide support.
  7. Some versions of the license say you cannot sell a copy of the software for more than the expense of distribution.

The license has two other obnoxious features:

  1. It has a very broad reverse license to AT&T, which goes far beyond the use of your code, even your code modified.
  2. It asserts one needs a license from AT&T to make a link to their web site. This is not an immediate practical problem, since the license says it gives permission to make such a link. (Anyway, people shouldn't make links to sites about non-free software.) But such a claim should not be made or propagated.

eCos Public License, version 1.1

This was the old license of eCos. It is not a free software license, because it requires sending every published modified version to a specific initial developer. There are also some other words in this license whose meaning we're not sure of that might also be problematic.

Today eCos is available under the GNU GPL with additional permission for linking with non-free programs.

GPL for Computer Programs of the Public Administration

The GPL-PA (whose original name in Portuguese is “Licença Pública Geral para Administração Pública”) is non-free for several reasons:

  • It permits use only in “normal circumstances”.
  • It does not allow distribution of source code without binaries.
  • Its permissions lapse after 50 years.
Hacktivismo Enhanced-Source Software License Agreement (HESSLA)

This is not a free software license, because it restricts what jobs people can use the software for, and restricts in substantive ways what jobs modified versions of the program can do.

Jahia Community Source License

The Jahia Community Source License is not a free software license. Use of the source code is limited to research purposes.

Old license of ksh93

ksh93 used to be shipped with an original license that was not a free software license. One reason for this is that it required that all changes be sent to the developer.

ksh93 is now released under the Common Public License.

License of Lha

The lha license must be considered non-free because it is so vague that you cannot be sure what permissions you have.

Microsoft Limited Public License (Ms-LPL)

This license is non-free because of section 3(F), which requires that any modified software you make from the original code must run on Windows. The Microsoft Public License does not have this restriction.

Microsoft Limited Reciprocal License (Ms-LRL)

This license is non-free because of section 3(G), which requires that any modified software you make from the original code must run on Windows. The Microsoft Reciprocal License does not have this restriction.

Microsoft Reference License

This is a non-free license: you are not allowed to modify the software at all, and you are only allowed to share it under very particular circumstances.

Microsoft's Shared Source CLI, C#, and Jscript License

This license does not permit commercial distribution, and only allows commercial use under certain circumstances.

Microsoft has other licenses which it describes as “Shared Source”, some of which have different restrictions.

Microsoft Windows Embedded CE 6.0 Shared Source License

This license is non-free because it places various limitations on the kinds of modifications you can make. For example, your modified software must run on Wince, and you are required to provide end user support for your software.

NASA Open Source Agreement

The NASA Open Source Agreement, version 1.3, is not a free software license because it includes a provision requiring changes to be your “original creation”. Free software development depends on combining code from third parties, and the NASA license doesn't permit this.

We urge you not to use this license. In addition, if you are a United States citizen, please write to NASA and call for the use of a truly free software license.

Open Public License

This is not a free software license, because it requires sending every published modified version to a specific initial developer. There are also some other words in this license whose meaning we're not sure of that might also be problematic.

License of PINE

The license of PINE is not a free software license because it mostly prohibits the distribution of modified versions. It also restricts the media that can be used for selling copies.

Please note that a successor to Pine, Alpine, is released under the Apache License, version 2.0.

Old Plan 9 license

This is not a free software license; it lacks essential freedoms such as the right to make and use private changes. Of course you should not use this license, and we urge you to avoid any software that has been released under it. A detailed discussion of this license is also available.

In September 2002 it was observed that the published license for Plan 9 had been modified, adding more restrictions to it, although its date still said 09/20/00. However, a further license change in 2003 made Plan 9 free software.

Reciprocal Public License

The Reciprocal Public License is a non-free license because of three problems. 1. It puts limits on prices charged for an initial copy. 2. It requires notification of the original developer for publication of a modified version. 3. It requires publication of any modified version that an organization uses, even privately.

Scilab license

This is not a free software license because it does not allow commercial distribution of a modified version. Thankfully, recent versions of the Scilab software are free software, released under CeCILL version 2.

Simple Machines License

Despite the name, this is a software license, and it's non-free for several reasons:

  • You must get the licensor's permission before distributing the software.
  • You cannot sell copies of the software.
  • It's possible that your license can be terminated if you received the software from someone who did not obey the license's terms.
Squeak license

As applied to software, this is not a free software license because it requires all users in whatever country to obey US export control laws. As applied to fonts, it also does not permit modification.

In addition, it has a requirement for users to indemnify the developer, which is enough to make many users think twice about using it at all.

Sun Community Source License

This is not a free software license; it lacks essential freedoms such as publication of modified versions. Please don't use this license, and we urge you to avoid any software that has been released under it.

Sun Solaris Source Code (Foundation Release) License, Version 1.1

This is not a free software license. The license prohibits redistribution, prohibits commercial use of the software, and can be revoked.

SystemC "Open Source" License, Version 3.0

This license requires all recipients to proactively help the licensor enforce its trademarks. This is an unreasonable condition to place on users' rights, so the license is non-free. It also has other practical problems: some of the requirements are vague, and it uses the term “intellectual property”.

Despite the name, this license has not been approved as an open source license as of this writing.

University of Utah Public License

The University of Utah Public License is a non-free license because it does not allow commercial redistribution. It also purports to restrict commercially running the software and even commercially giving consultation about it. Those restrictions are probably not legally enforceable under US copyright law, but they might be in some countries; even asserting them is outrageous.

The use of this license by the University of Utah exemplifies a dangerous trend for universities to restrict knowledge rather than contributing it to the public.

If a university tries to impose a license like this on the software you are writing, don't give up hope. With persistence and firmness, and some forethought, it is possible to prevail over money-grabbing university administrators.

The earlier you raise the issue, the better.

YaST License

This is not a free software license. The license prohibits distribution for a fee, and that makes it impossible for the software to be included in the many CD-ROM free software collections that are sold by companies and by organizations such as the FSF.

There may be another problem in section 2a, but a word seems to be missing there, so it is hard to be sure what meaning is really intended.

(The YaST software itself no longer uses this non-free YaST license; happily, it is now free software, released under the GNU GPL.)

Licenses For Documentation

Free Documentation Licenses

The following licenses qualify as free documentation licenses.

GNU Free Documentation License

This is a license intended for use on copylefted free documentation. We plan to adopt it for all GNU manuals. It is also suitable for other kinds of useful works (such as textbooks and dictionaries, for instance). Its applicability is not limited to textual works (“books”).

Apple's Common Documentation License, Version 1.0

This is a Free Documentation license that is incompatible with the GNU FDL. It is incompatible because Section (2c) says “You add no other terms or conditions to those of this License”, and the GNU FDL has additional terms not accounted for in the Common Documentation License.

FreeBSD Documentation License

This is a permissive non-copyleft free documentation license that is compatible with the GNU FDL.

Open Publication License, Version 1.0

This license can be used as a free documentation license. It is a copyleft free documentation license provided the copyright holder does not exercise any of the “LICENSE OPTIONS” listed in Section VI of the license. But if either of the options is invoked, the license becomes non-free. In any case, it is incompatible with the GNU FDL.

This creates a practical pitfall in using or recommending this license: if you recommend “Use the Open Publication License, Version 1.0 but don't enable the options”, it would be easy for the second half of that recommendation to get forgotten; someone might use the license with the options, making a manual non-free, and yet think he or she is following your advice.

Likewise, if you use this license without either of the options to make your manual free, someone else might decide to imitate you, then change his or her mind about the options thinking that that is just a detail; the result would be that his or her manual is non-free.

Thus, while manuals published under this license do qualify as free documentation if neither license option was used, it is better to use the GNU Free Documentation License and avoid the risk of leading someone else astray.

Please note that this license is not the same as the Open Content License. These two licenses are frequently confused, as the Open Content License is often referred to as the “OPL”. For clarity, it is better not to use the abbreviation “OPL” for either license. It is worth spelling their names in full to make sure people understand what you say.

Non-Free Documentation Licenses

The following licenses do not qualify as free documentation licenses:

Open Content License, Version 1.0

This license does not qualify as free, because there are restrictions on charging money for copies. We recommend you do not use this license.

Please note that this license is not the same as the Open Publication License. The practice of abbreviating “Open Content License” as “OPL” leads to confusion between them. For clarity, it is better not to use the abbreviation “OPL” for either license. It is worth spelling their names in full to make sure people understand what you say.

Open Directory License (aka dmoz.org License)

This is not a free documentation license. The primary problems are that your right to redistribute any given version is not permanent and that it requires the user to keep checking back at that site, which is too restrictive of the user's freedom.

Licenses for Works of Practical Use Besides Software and Documentation

GNU General Public License

The GNU GPL can be used for general data which is not software, as long as one can determine what the definition of “source code” refers to in the particular case. As it turns out, the DSL (see below) also requires that you determine what the “source code” is, using approximately the same definition that the GPL uses.

GNU Free Documentation License

The GNU FDL is recommended for textbooks and teaching materials for all topics. (“Documentation” simply means textbooks and other teaching materials for using equipment or software.) We also recommend the GNU FDL for dictionaries, encyclopedias, and any other works that provide information for practical use.

Creative Commons Attribution 2.0 license (a.k.a. CC-BY)

This is a non-copyleft free license that is good for art and entertainment works, and educational works. Please don't use it for software or documentation, since it is incompatible with the GNU GPL and with the GNU FDL.

Creative Commons publishes many licenses which are very different. Therefore, to say that a work “uses a Creative Commons license” is to leave the principal questions about the work's licensing unanswered. When you see such a statement in a work, please ask the author to highlight the substance of the license choices. And if someone proposes to “use a Creative Commons license” for a certain work, it is vital to ask immediately, “Which one?”

Creative Commons Attribution-Sharealike 2.0 license (a.k.a. CC-BY-SA)

This is a copyleft free license that is good for artistic and entertainment works, and educational works. Please don't use it for software or documentation, since it is incompatible with the GNU GPL and with the GNU FDL.

Please be specific about which Creative Commons license is being used.

Design Science License (DSL)

This is a free and copyleft license meant for general data. Please don't use it for software or documentation, since it is incompatible with the GNU GPL and with the GNU FDL; however, it is fine to use for other kinds of data.

Free Art License

This is a free and copyleft license meant for artistic works. It permits commercial distribution, but any larger work including the copylefted work must be free. Please don't use it for software or documentation, since it is incompatible with the GNU GPL and with the GNU FDL.

Licenses for Fonts

The licenses below apply to an instantation of a design in a computer file, not the artistic design. As far as we know, an implementation of a design is always copyrightable. The legal status of the artistic design is complex, and varies by jurisdiction.

GNU General Public License

The GNU GPL can be used for fonts. However, note that it does not permit embedding the font in a document unless that document is also licensed under the GPL. If you want to allow this, use the font exception. See also this explanatory essay about the GPL Font Exception.

Arphic Public License

This is a copyleft free software license, incompatible with the GPL. Its normal use is for fonts, and in that use, the incompatibility does not cause a problem.

SIL Open Font License 1.1

The Open Font License (including its original release, version 1.0) is a free copyleft license for fonts. Its only unusual requirement is that fonts be distributed with some computer program, rather than alone. Since a simple Hello World program will satisfy the requirement, it is harmless. Neither we nor SIL recommend the use of this license for anything other than fonts.

Licenses for Works of Opinion and Judgment

Works that express someone's opinion—memoirs, editorials, and so on—serve a fundamentally different purpose than works for practical use like software and documentation. Because of this, we expect them to provide recipients with a different set of permissions: just the permission to copy and distribute the work verbatim. Richard Stallman discusses this frequently in his speeches.

Because so many licenses meet these criteria, we cannot list them all. If you are looking for one to use yourself, however, there are two that we recommend:

GNU Verbatim Copying License

This is the license used throughout the GNU and FSF web sites. It is very simple, and especially well-suited to written works.

Creative Commons Attribution-NoDerivs 3.0 license (a.k.a. CC-BY-ND)

This license provides much the same permissions as our verbatim copying license, but it's much more detailed. We particularly recommend it for audio and/or video works of opinion. Please be specific about which Creative Commons license is being used.

More about licenses.

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