But still if you own the software then its legal.
Apple can try to go something about it but it wouldn't hold up.
Plus I don't think apple is really worried about people putting osx on their computers. They are more worried about companies like pystar that are selling apple clones.
Remember, you never "own" the software these days, you have purchased permission to use it.
That's the kind of stuff that started pushing me to Linux years ago. I got Vista and am testing Windows 7, but it would take a LOT to make Windows or OSX my main OS now.