>Why is making a kernal extension allowed then?
Because the kernel is open source. Apple obviously has a different licensing policy for their open source code. Where the open source ends and the closed begins is at a certain closed-source kernel module which checks to see if it's running on a genuine Apple machine. If it is, it'll happily decrypt the Finder and Dock binaries during runtime. If not, well, then you just have a really nice Unix shell.

>Still anything is possible with a good lawyer.
Just curious, would you say that software piracy is a grey area of the law?

This is really an non argument Apple sells it's computers them self or through authorized stores, like the booths at Best Buy. If you did not get one either of those 2 ways it is not licensed hardware . Still like it has been said before you either hacked the software or downloaded a hacked version. Both are illegal in most countries. If you like Mac so much consider buying one but if you just hate PC get Linux (Free) and a theme that looks like OSX. No legal issues there.

No, not piracy, but usage rights.
Zak, you're right it's not an argument....

Until the agreement is argued in court it is still breech of contract and reverse engineering, which is all hacking really is, is still illegal as well. And of course copyright if you are sharing it. I am not sure if you bought a real copy and downloaded the modified copy if that is illegal. The court does not know either.