It seems like there is a hacked version of Mac OS that runs on non Apple computers. It's called kalyway, and is out there on the torrentsphere. Ok, if not already, it will soon be crippled on a future update, but what the heck, it's fun!
If I had not bought an iMac I'd probably give it a try. As I've written so many times, Mac OS X is a great OS and should be allowed to compete on a free and transparent market. You should go ahead and free Mac OS, Mr. Jobs, if not for other reason, just to annoy me (now that I bough a Mac...) :P