Various Licenses and Comments about Them – GNU Project – Free Software Foundation

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.

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.

This is the latest version of the LGPL: a free software license, but not
a strong copyleft license, because it permits linking with nonfree
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.

This is the previous version of the LGPL: a free software license,
but not a strong copyleft license, because it permits linking with
nonfree 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.

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.

This is a lax, 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.

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

Please note that this license is not compatible with GPL version 2,
because it has some requirements that are not in that GPL version.
These include certain patent termination and indemnification
provisions. The patent termination provision is a good thing, which
is why we recommend the Apache 2.0 license for substantial programs
over other lax permissive licenses.

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

This license is a free software license, compatible with the GPL. It
is the minimal set of changes needed to correct the vagueness of the Artistic License 1.0.

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

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

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

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

The modified BSD license is not bad, as lax permissive licenses go,
though the Apache 2.0 license is preferable. However, it is risky to
recommend use of “the BSD license”, even for special cases
such as small programs, 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 modified BSD license are
more or less equivalent.

However, the Apache 2.0 license is better for substantial programs,
since it prevents patent treachery.

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”
and
“protection”; 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.

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 refusing users patent licenses to set up a trap
for you, it would be wise to avoid the program.

This is a lax, permissive non-copyleft free software license,
compatible with the GNU GPL. It is nearly identical to the FreeBSD (also
called “2-clause BSD”) license.

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.

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.

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

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

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

Some people call this license “the MIT License,” but
that term is misleading, since MIT has used many licenses for
software. It is also ambiguous, since the same people also call
the X11 license “the MIT License,”
failing to distinguish them. We recommend not using the term “MIT
License.”

The difference between the X11 license and the Expat license is
that the X11 license contains an extra paragraph about using the X
Consortium’s name. It is not a big deal, but it is a real
difference.

For substantial programs it is better to use the Apache 2.0 license
since it blocks patent treachery.

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 lax, permissive
non-copyleft free software license, compatible with the GNU GPL.

Our comments about the Modified BSD license
apply to this license too.

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

This is a lax, permissive, and weak free software license that is
compatible with the GPL. It is similar to the license of Python 1.6a2 and earlier versions.

This is a free software license and is GPL compatible.

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.

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.

An “informal license” means a statement such as
“do whatever you like with this” or “you can
redistribute this code and change it.”

In the United States, these licenses are supposed to be interpreted
based on what the author seems to intend. So they probably mean what
they appear to mean. That would make them non-copyleft free software
licenses and compatible with the GNU GPL. However, an unlucky choice
of wording could give it a different meaning.

However, many other countries have a more rigid approach to
copyright licenses. There is no telling what courts in those
countries might decide an informal statement means. Courts might
even decide that it is not a license at all.

If you want your code to be free, don’t invite gratuitous trouble
for your users. Please choose and apply an established free software
license. We offer
recommendations that we suggest you follow.

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

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

This license had an unfortunate wording choice: it provided recipients with “Permission to use, copy, modify, and distribute this software…” This was 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. ISC also updated the license to read “Permission to use, copy, modify, and/or distribute this software…” While the inclusion of “and/or” doesn’t completely solve the issue, 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 FreeBSD License is similarly permissive and brief. However, if you want a lax, weak license, we recommend using the Apache 2.0 license.

This is a free software license. Section 3.3 provides indirect
compatibility between this license and the GNU GPL version 2.0, the
GNU LGPL version 2.1, the GNU AGPL version 3, and all later versions
of those licenses. When you receive work under MPL 2.0,
you may make a “Larger Work” that combines that work with
work under those GNU licenses. When you do, section 3.3 gives
you permission to distribute the MPL-covered work under the terms of
the same GNU licenses, with one condition: you must make sure that the
files that were originally under the MPL are still available under the
MPL’s terms as well. In other words, when you make a combination this
way, the files that were originally under the MPL will be dual
licensed under the MPL and the GNU license(s). The end result is that
the Larger Work, as a whole, will be covered under the GNU license(s).
People who receive that combination from you will have the option to
use any files that were originally covered by the MPL under that
license’s terms, or distribute the Larger Work in whole or in part
under the GNU licenses’ terms with no further restrictions.

It’s important to understand that the condition to distribute files
under the MPL’s terms only applies to the party that first creates and
distributes the Larger Work. If it applied to their recipients as well, it
would be a further restriction and incompatible with the GPL and AGPL.
That said, when you make contributions to an existing project, we usually
recommend that you keep your changes under the same license,
even when you’re not required to do so. If you receive a work under a GNU
license where some files are also under the MPL, you should only remove the
MPL from those files when there’s a strong reason to justify it.

Check the license notices on the MPL-covered software before you make
a Larger Work this way. Parties who release original work under
MPL 2.0 may choose to opt out of this compatibility by
including a sentence in the license notices that says that the work is
“Incompatible With Secondary Licenses.” Any software that
includes this notice is not compatible with the GPL
or AGPL.

Software under previous versions of the MPL can be upgraded to version
2.0, but any software that isn’t already available under one of the
listed GNU licenses must be marked as Incompatible With Secondary
Licenses. This means that software that’s only available under
previous versions of the MPL is still incompatible with the GPL and AGPL.

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

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

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.

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.

If you want to release your work to the public domain, we encourage
you to use formal tools to do so. Our solution is to ask people who
make small contributions to GNU to sign a disclaimer form. If you’re
working on a project that doesn’t have formal contribution policies,
contact the project to discuss how best to contribute within the
project’s licensing model.

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).

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).

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

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.

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

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
lax 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 lax permissive license for your project, please use
the Expat license for a small program and the
Apache 2.0 license for a substantial program. These are far more
common, and widely recognized in the free software community.

This is a lax, permissive non-copyleft free software license, compatible
with the GNU GPL. The license does provide the ability to license
patents along with the software work, however, we still recommend the
Apache 2.0 license for avoiding patent treachery when choosing to put
your work under a lax license.

The Unlicense is a public domain dedication. A work released
under the Unlicense is dedicated to the public domain to the fullest
extent permitted by law, and also comes with an additional lax
license that helps cover any cases where the dedication is inadequate.
Both public domain works and the lax license provided by the
Unlicense are compatible with the GNU GPL.

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

This is a free software license and is GPL compatible.

Google’s WebM implementation is covered by the Modified BSD License. Google also provides a
separate patent license (confusingly called an “Additional IP
Rights Grant”) for patents that Google owns or controls that are
necessarily infringed by their implementation of WebM. GPL-covered
software can be distributed in compliance with this license’s terms: it
allows distributors to exercise all of the rights granted by the GPL,
while fulfilling all its conditions. Thus, all of WebM’s license is
free and GPL-compatible.

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

We do not recommend this license. If you want a lax permissive
license for a small program, we recommend
the X11 license. A larger program usually
ought to be copyleft; but if you are set on using a lax permissive
license for one, we recommend the Apache 2.0 license since it protects
users from patent treachery.

The WxWidgets license is a GPL-compatible free software license. It
consists of the GNU
Lesser GPL 2.0 or any later version, plus an additional permission
allowing binary distributions that use the library to be licensed
under terms of the distributor’s choice (including proprietary). It
is a weak copyleft, even weaker than the LGPL, so we recommend
it only in special
circumstances.

An older name for the WxWidgets Library license.

This is a lax 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.

Some people call this license “the MIT License,” but
that term is misleading, since MIT has used many licenses for
software. It is also ambiguous, since the same people also call
the Expat license “the MIT License,”
failing to distinguish them. We recommend not using the term “MIT
License.”

The difference between the X11 license and the Expat license is
that the X11 license contains an extra paragraph about using the X
Consortium’s name. It is not a big deal, but it is a real
difference.

This is a fine license for a small program. A larger program
usually ought to be copyleft; but if you are set on a lax permissive
license for one, we recommend the Apache 2.0 license since it protects
users from patent treachery.

This is a lax, 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.

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

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