There aren't any developers left who own an Apple computer. However, some skilled SG enthusiasts attempted to cross-compile the Smokin'Guns executables on Linux for MAC OS X.
You would need to download and extract the OS independent archive, which, as you figured out, does not include MAC OS X executables. Then you would need to copy MAC OS X executables provided by someone else into that folder.
Read these threads:
Smokin'Guns is open source. When in doubt, compile the executable and provide an installer yourself. In case you object that you don't know how to do that - well, the same holds for me, too.