Not as much as you might think. OSX will install on a PC, but Apple makes it almost impossible to run their code on anything not theirs.
No..., I think you got it backwards from what I was saying ... :-) When you run Mac OS X on a non-Macintosh machine -- you don't have a Macintosh. What I was talking about -- is -- when you have a Macintosh -- and that's when you find that you can run it all ... you see. That's the machine to get... doncha know ...
And, as far as Apple making it near impossible to run their software (the Mac OS X) on any other machine besides a Macintosh -- that's exactly what Apple should do -- make it literally impossible to run their operating system software on any other machine not made by them.
That's because Apple is in the business of making hardware -- and the software is a "give-away" item to support their hardware and make it something with a better user experience than other machines.
It wouldn't "pay" Apple to have "give-away software" (like the Mac OS X, which is not their main line of business) -- and hand that software out to other generic boxes which they don't make. To do that is a sure way for a company like Apple (who has designed their business around "hardware") to go completely bankrupt in short order. That wouldn't do them or their customers any good ... doncha know ... :-)
Remember Orange Computer and the Mac clones of the mid-1990s?