Published software should be free software. To make it free software, you need to release it under a free software license. We normally use the GNU General Public License (GNU GPL), but occasionally we use other free software licenses. We use only licenses that are compatible with the GNU GPL for GNU software.

Documentation for free software should be free documentation, so that people can redistribute it and improve it along with the software it describes. To make it free documentation, you need to release it under a free documentation license. We normally use the GNU Free Documentation License (GNU FDL), but occasionally we use other free documentation licenses.

If you've started a new project and you're not sure what license to use, “How to choose a license for your own work” details our recommendations in an easy-to-follow guide. If you just want a quick list reference, we have a page that names our recommended copyleft licenses.

We also have a page that discusses the BSD License Problem.