Let's see. Checklist for whether the EULA is recognizable as a valid contract.

Does the buyer get to negotiate? Nope.

Does Apple end up with a written copy, signed by the buyer, that can subsequently serve as legal evidence that the buyer agreed to Apple's terms? Nope.

Does the buyer get anything in exchange for accepting the restrictions of the so-called agreement? Nope.

Let's break that last down.

Does the buyer get a copy of the software in exchange for accepting the restrictions? Nope, the buyer gets a copy in exchange for money at some retail outlet, either installed on a machine or on a disk in a shrink-wrapped box, without having to agree to anything or sign anything first.

Does the buyer get the right to install the software? Nope, the buyer already has that right as soon as they have a copy purchased in good faith, and they have exactly such a copy. They may even already have an installed copy, but even if they just have a disk in a shrink-wrapped box, USC Title 17 Section 107(a)(1) clearly permits them to make whatever private copies are normal as part of software installation and use, without requiring the explicit permission of the copyright holder.

The most the buyer gets is a warranty or something that they can, perhaps, do without. (And in my experience, software always comes with explicit disclaimers of any warranties anyway.)

It seems that the answer here is clear. Psystar might be in breach of some contract, or even may have infringed copyright. Individual users certainly have not infringed copyright, even if they buy OS X separately and install it on a Psystar b0x, per the above, and, also per the above, they have not breached a (valid!) contract either.

Apple's sole legitimate recourse is to refuse to support OS X on hardware other than that for which it was designed; for that, they're well within their rights (and if it's compatibility headaches they're worried about, rather than, say, monopoly rents on hardware-that-will-run-OSX, it's the smart thing for them to do).

Disclaimer: I'm not claiming that no court in the land will convict. I'm just claiming that if any of them do, then they got it wrong. It's happened before, unfortunately.

P.S. "Which of the following is a color?
Avocado, Spaniel, Guava, Whippet, Virginia, Maroon" -- At least two correct answers, Avocado and Maroon, and it didn't accept Maroon. It also didn't reject it. It said, instead, that the field had been left blank! Fix your broken captcha quickly please.