Some guys over at the Georgia Institute of Technology have done the unthinkable! They have gotten OS X (under PearPC) to run on a modded XBOX and you can too
Things you need
-Copy of OS X
-Latest Version of PearPC
Basically what you’re going to be doing is installing Xebian Linux on your modded xbox. Then you can download and install PearPC which will allow you to Install and Run OS X on your XBOX. Then presto chango 10-12 hours later thanks to the miracle of Emulation you have OS X running on the slowest hardware possible.
for the complete set of instructions visit http://www.cc.gatech.edu/~ranma1/mac_install.html