You can play the PC version on the mac. Just download the RenPy dev kit from
You must be registered to see the links
.
During setup you'll be asked to pick a project directory, if you set that to the directory where you have all the unzipped files, you'll be able to "Launch Project" on the Mac with the PC version and it will most likely run. (Summer with Mia runs no problem)
The only problems I've ever had is when the dev does something against the rules and tries to write files in random places.