The files in this repository are released under standard open source
licenses, identified by SPDX license tags. Generally, kernel-level
code is licensed under GPLv2 and user-level code under the 2-clause BSD
license. See the individual file headers for details, or use one of the
publicly available SPDX tools to generate a bill of materials. The
directory LICENSES contains the text for all licenses that are
mentioned by files in this repository.
Note that, as in the Linux syscall note for the GPL, the seL4 kernel GPL license does not cover user-level code that uses kernel services by normal system calls - this is merely considered normal use of the kernel, and does not fall under the heading of "derived work". Syscall headers are provided under BSD.
For a longer explanation of how the seL4 license does or does not affect your own code see also this blog post.