I think they were looking into finding an equivalent for .dlls on the Mac and they found out that there is no such implementation in place for the Mac version of Q3A. Mod users were told to use the virtual machine which automatically allows cross-platform compatibility, but PC users quickly learned that it's slower than the previously-used .dlls. I think id Software probably also realized that sacrificing speed for easy cross-platform compatibility wasn't worth it for the majority of their customers (PC users) and thus will be returning to .dlls for the new Doom game (which will also run on Mac OS X).
Anyway, you might want to try Rocket Arena for Unreal Tournament.