Sorry to say it is a basic problem, the game in question is compiled to run on Intel /AMD style chips, so even with X11 you will not be able to run the game because it is in the wrong file format. X11 only does the display, your Mac still has to read the file itself.
Best chance lobby the developer and get them to compile it for PowerPC aka Mac under X11 or even better under OpenGL for the Mac.
Bummer Dude