Yep, Ubuntu, etc
You can run Mac OS X 10.9, Windows 8 and Ubuntu on the same Mac, either booting through EFI or in virtual machines: Parallels, VMWare
Ugh, virtualization? Why bother on a desktop unless you're actually planning on using the underlying OS as well, or if you have to run a crappy OS (Windows) and would prefer it to run on top aof a good OS. Via EFI means native though right? Will have to read up on that.