There is a strange issue that makes it not work on the Mac at all, whether you have full support for GLSL or not.
The error is known, but the cause for it is a completely mystery. The shaders just appear to become invalidated for unknown reasons once you are all the way in the game. I have tried everything that I can think of but nothing appears to work. I assume that it's something that the Mac drivers do that doesn't happen on other platforms, but I have yet to figure out what it is.
My hardware doesn't support GLSL and that makes it a very difficult, and extremely slow, thing to fix.