Think of it this way. If I legally purchased a copy of OS X and installed it on my own Hackintosh system, Apple is not going to enforce the EULA in regards to your own personal use. But, and this is addressed to everyone who says Psystar is perfectly within their rights to sell computers with OS X pre-installed, that's not what Psystar was doing. They are using it to make a profit. The home user, who does it on their own, has every right to do so, because Apple will not claim violation of the EULA, because the user who does it for their own personal preference isn't selling Apple's software without paying licensing fees to Apple. But Psystar did, whether preinstalled or not, and that is the problem.
Even if Psystar legally purchased every copy of OS X they installed or shipped with their Open Computer, they are still not within their rights.
As a filmmaker, if I make a film, and I want to put a Springsteen song FROM A CD THAT I OWN (thus, the COPY of the song is mine) on the soundtrack, I can, and Springsteen and the record label won't care, UNTIL I decide to release the film to market and sell tickets. I am legally obligated to pay for the rights to do so, both to the record label and the publishing company, and in some cases the artist as well. Why? Because it is not my intelletual property to do with as I please.
So, the argument that Psystar could do whatever they wanted, even if they paid for each copy, is wrong. Not necessarily logical, or even fair, but still illegal.