“The GNU Public License and licenses modeled on it impose the restriction that source code must be distributed or made available for all works that are derivatives of the GNU copyrighted code.
While this may superficially look like a noble strategy, it is a condition that is typically unacceptable for commercial use of software. So in practice, it usually ends up hindering free sharing and reuse of code and ideas rather than encouraging it. As a consequence, no additional software bound by the GPL terms will be considered for inclusion into the OpenBSD base system.”
As to clang’s Address Sanitizer, that’s under the Apache License v2.0 with LLVM Exceptions (https://github.com/google/sanitizers/blob/master/LICENSE.TXT), of which the same page says:
“The original Apache license was similar to the Berkeley license, but source code published under version 2 of the Apache license is subject to additional restrictions and cannot be included into OpenBSD. In particular, if you use code under the Apache 2 license, some of your rights will terminate if you claim in court that the code violates a patent.”