- OpenBSD's BSD license (Berkeley)
- Apache 1.x licenses***
- Caldera (BSD 4-clause license)
- GNU (L)GPL*
- Public Domain
- Apache 2.x licenses***
* The (L)GPL license is disallowed in the kernel or runtime.
** X is distributed with many OpenBSD ports as a convenience to the user, subject to applicable license terms.
*** The version of Apache coming with OpenBSD is a Compiled Work and not a Derivatived Work. Apache 2 licenses say with OpenBSD's Apache version is a Derivatived Work. Apache 2 licenses thus can't be used in OpenBSD.