The first mailing list post is a pretty good dive: http://lists.llvm.org/pipermail/llvm-dev/2015-October/091536.html http://lists.llvm.org/pipermail/llvm-dev/20

The first mailing list post is a pretty good dive: http://lists.llvm.org/pipermail/llvm-dev/2015-October/091536.html http://lists.llvm.org/pipermail/llvm-dev/2015-October/091536... In particular, the Apache license is a very clear and more importantly very well-accepted mechanism of licensing relevant patents and not irrelevant ones. The BSD and MIT licenses may or may not license patents depending on how you (or the courts, really) interpret "Permission to use ... is hereby granted ...." They also had a custom scheme for dual-licensing the runtime libraries that get linked into compiled binaries. The new scheme grants a non-attribution license based on the fact that it ended up in your code after running clang, not which repo it was in, which makes it easier for LLVM to refactor code between repos.