That is interesting as I have a user on steam using this version and even though Steam has a general warning about it, it worked fine. - so I had not researched the issue.
The game does create both a log for Unity and a log for the game program itself I am not sure where Mac would put the Unity log (which is probably what we need), but the game logs are in <Game Data Directory> /logs . I suspect the Unity log is near the actual binary package. I would be curious if there as any output at all.
Is there anyway you can look for them?
Evidently, this may have something to do with Apple insisting devs have their apps signed by Apple, even if the app is functional otherwise. Your PC is becoming a console. That sucks.
Do me another favor if you have a Steam account, and see if you can get it running via that means (I suspect you can).
send me an email at mok@killerbeesoftware.com and we can discuss more as a solution will need testing.
--Mark