Uh. A GUI (Graphical User Interface), whether it's for a game or an operating system is only as hard as you make it (or, in some extreme Windows-only Registry hacking cases, break it).
There is a commerical convert of WINE that supports DirectX -> OpenGL. Also, with WINE & copies, you need to get your hands on some of the Windows DLLs required to work. I think I made a list of them and described about half of them somewhere on this forum... Erm.... (try searching for '.DLL'
)
Anyway, there's quite a few BASIC-based languages for Linux available. Just remember what I found out the hard way - you can't install any RPM-programs even temporarily on a MandrakeMove (bootable-CDROM) distribution
[img src=http://blanky.pt-web.net/ddd.gif] >::p