How to choose a license for your own work
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People often ask us what license we recommend they use for their
project. We've written about this publicly before, but the
information has been scattered around between different essays, FAQ
entries, and license commentaries. This article collects all that
information into a single source, to make it easier for people to
follow and refer back to.
These recommendations are for works designed to do practical jobs.
Those include software, documentation, and some other things. Works of
art, and works that state a point of view, are different issues; the GNU
Project has no general stand about how they should be released, except
that they should all be usable without nonfree software (in
particular, without DRM).
However, you might want to follow these recommendations for art works
that go with a particular program.
The recommendations apply to licensing a work that you
create—whether that's a modification of an existing work, or a
new original work. They do not address the issue of combining
existing material under different licenses. If you're looking for
help with that, please check our GPL
After you see what we recommend here, if you'd like advice, you can
Note that it will probably take a few weeks for the licensing team to
get back to you; if you get no response in a month, please write
Contributing to an existing project
When you contribute to an existing project, you should usually release
your modified versions under the same license as the original work.
It's good to cooperate with the project's maintainers, and using a
different license for your modifications often makes that cooperation
very difficult. You should only do that when there is a strong reason
to justify it.
One case where using a different license can be justified is when you make
major changes to a work under a non-copyleft license. If the version you've
created is considerably more useful than the original, then it's worth
copylefting your work, for all the same
reasons we normally recommend
copyleft. If you are in this situation, please follow the
recommendations below for licensing a new project.
If you choose to release your contributions under a different
license for whatever reason, you must make sure that the original
license allows use of the material under your chosen license. For
honesty's sake, show explicitly which parts of the work are under
We recommend different licenses for different projects, depending
mostly on the software's purpose. In general, we recommend using the
strongest copyleft license that doesn't interfere with that purpose.
Our essay “What
is Copyleft?” explains the
concept of copyleft in more detail, and why it is generally the best
For most programs, we recommend that you use the most recent
version of the GNU General Public License
(GPL) for your project. Its strong copyleft is appropriate for
all kinds of software, and includes numerous protections for users'
Now for the exceptions.
It is not worth the trouble to use copyleft for most small
programs. We use 300 lines as our benchmark: when a software
package's source code is shorter than that, the benefits provided by
copyleft are usually too small to justify the inconvenience of making
sure a copy of the license always accompanies the software.
For those programs, we recommend
License 2.0. This is a pushover (non-copyleft) software license
that has terms to prevent contributors and distributors from suing for
patent infringement. This doesn't make the software immune to threats
from patents (a software license can't do that), but it does prevent
patent holders from setting up a “bait and switch” where
they release the software under free terms then require recipients to
agree to nonfree terms in a patent license.
Among the lax pushover licenses, Apache 2.0 is best; so if you
are going to use a lax pushover license, whatever the reason,
we recommend using that one.
For libraries, we distinguish three kind of cases.
Some libraries implement free standards that are competing against
restricted standards, such as Ogg Vorbis (which competes against MP3
audio) and WebM (which competes against MPEG-4 video). For these
projects, widespread use of the code is vital for advancing the cause
of free software, and does more good than a copyleft on the project's
code would do.
In these special situations, we recommend
For all other libraries, we recommend some kind of copyleft. If
developers are already using an established alternative library
released under a nonfree license or a lax pushover license, then we
recommend using the GNU Lesser General
Public License (LGPL).
Unlike the first case, where the library implements an ethically
superior standard, here adoption for its own sake will not accomplish
any special objective goal, so there's no reason to avoid copyleft
entirely. However, if you require developers who use your library to
release their whole programs under copyleft, they'll simply use one of
the alternatives available, and that won't advance our cause either.
The Lesser GPL was designed to fill the middle ground between these
cases, allowing proprietary software developers to use the covered
library, but providing a weak copyleft that gives users freedom
regarding the library code itself.
For libraries that provide specialized facilities, and which do not
face entrenched noncopylefted or nonfree competition, we recommend
using the plain GNU GPL. For the reasons why,
read “Why you shouldn't
use the Lesser GPL for your next library”.
If it is likely that others will make improved versions of your
program to run on servers and not distribute their versions to anyone
else, and you're concerned that this will put your released version at
a disadvantage, we recommend the GNU
Affero General Public License (AGPL). The AGPL's terms are almost
identical to the GPL's; the sole substantive difference is that it has
an extra condition to ensure that people who use the software over a
network will be able to get the source code for it.
The AGPL's requirement doesn't address the problems that can arise
for users when they entrust their computing or their data to
someone else's server. For instance, it won't stop
as a Software Substitute (SaaSS) from denying users'
freedom—but most servers don't do SaaSS. For more about these
issues, read “Why the
We recommend the GNU Free
Documentation License (GFDL) for tutorials, reference manuals and
other large works of documentation. It's a strong copyleft license
for educational works, initially written for software manuals, and
includes terms which specifically address common issues that arise
when those works are distributed or modified.
For short, secondary documentation works, such as a reference card,
it is better to use
all-permissive license, since a copy of the GFDL could hardly fit
in a reference card. Don't use CC-BY, since it is incompatible with
For man pages, we recommend the GFDL if the page is long, and
all-permissive license if it is short.
Some documentation includes software source code. For instance, a manual
for a programming language might include examples for readers to follow.
You should both include these in the manual under the FDL's terms, and
release them under another license that's appropriate for software. Doing
so helps make it easy to use the code in other projects. We recommend that
you dedicate small pieces of code to the public domain using CC0, and
distribute larger pieces under the same license that the associated
software project uses.
Other data for programs
This section discusses all other works for practical use that you
might include with software. To give you some examples, this includes
icons and other functional or useful graphics, fonts, and geographic
data. You can also follow them for art, though we wouldn't criticize
if you don't.
If you are creating these works specifically for use with a software
project, we generally recommend that you release your work under the
same license as the software. There is no problem in doing so
with the licenses we have recommended:
GPLv3, LGPLv3, AGPLv3, and GPLv2 can all be applied to any kind of
work—not just software—that is copyrightable and has a clear
preferred form for modification. Using the same license as the
software will help make compliance easier for distributors, and avoids
any doubt about potential compatibility issues. Using a different
free license may be appropriate if it provides some specific practical
benefit, like better cooperation with other free projects.
If your work is not being created for use with a particular software
project, or if it wouldn't be appropriate to use the same license as
the project, then we only recommend that you choose a copyleft license
that's appropriate for your work. We have some of these listed on
our license list. If no license seems especially
appropriate, the Creative Commons Attribution-ShareAlike
license is a copyleft that can be used for many different kinds of