The seL4 kernel itself and most of its proof is licensed under GPL Version 2. For full terms and conditions, see the file LICENSE_GPLv2.txt in the seL4 repository. As for Linux, the GPL applies to the kernel itself, not to user-level programs running on top of it.

Various further components, libraries, and tools are released under the 2-clause BSD license. For details see the file LICENSE_BSD2.txt in the respective repositories. See the individual file headers for which license applies to which file.

Additionally, the release contains 3rd-party open-source software, available under standard open-source licenses such as GPLv2, 3-clause BSD, and MIT/Expat. See the individual file headers for details.

All code is hosted on github, available at