It does "work", but it is quite old and has no support for AES-GCM. The advantage of using OpenSSL's AES-GCM implementation (instead of our own) is that they leverage the AES-NI instruction set of current Intel CPUs, making it quite a bit faster.
Since speed in AES-GCM processing is mainly important when used together with the `--with-suite-b` option, which processes IPsec packets in userland in order to bring support for that algorithm to Mac OS X (because the IPsec stack in the kernel does not support it), I could make the OpenSSL dependency conditional on that option (and use our own gcm implementation if it is not enabled).