Here's another post by Mark Rein's top dog @Epic Games Inc

Linux is now up and running pretty well. I've been told that we should be able to release the Linux client and server executables around the same time as the windows version ships. Official tech support isn't provided for the Linux versions. Currently Linux will only work well with Nvidia cards - apparently ATI's OpenGL Linux and Mac drivers don't support texture compression. Hopefully this is something they will soon fix. Mac development is just underway so it will still be a little while before it's done. Here's the full thread if you want to read it! Click Here