I just want to clarify about Episode 5:
As I've summed up in detail here, Episode 5 is very much alive nad being worked on.
Though we love Chris and his years of support, he's not actually on the team at this point, so his info is a little outdated.
Episode 5 will have a Mac port, but as for Episode 1-4, unfortunately, the Mac port is highly unlikely to happen. The engine they were built is old, outdated, no longer supported by the people who made it, and we have no one on the team familiar enough with both it and Macs to make those ports. We're putting our focus on getting Episode 5 done (as well as our other projects, but as explained in the post I linked to above, those are different teams) instead.
A lot of people have been able to play it on their Macs using the suggestions given in the thread that Weldon (wilco) linked to in his post above, though.