Mac OS X is not supported.
Neither are the OSS drivers. Right now it requires the compatibility contexts, which means it's limited to the NVidia and AMD proprietary drivers on Windows and Linux only.
Originally Posted by trebor
That is not entirely true anymore. Mac OS X support was patched in last week and you can run the game with OSS drivers if you start it with +set r_useOpenGL32 0.
However better Mesa support is in the works. There are only a few changes left. See https://github.com/RobertBeckebans/R...BFG/issues/107