You can use Apache 2.0 license with the "LLVM exception", which was made to deal with the GPL2 compatibility issue (though the LLVM exception is relatively rece

You can use Apache 2.0 license with the "LLVM exception", which was made to deal with the GPL2 compatibility issue (though the LLVM exception is relatively recent, maybe it didn't exist or openssl weren't aware of it at the time). See e.g. https://spdx.org/licenses/LLVM-exception.html https://spdx.org/licenses/LLVM-exception.html . Used by at least LLVM and CUPS.