I Say Anything that involves Installing OSX on anything but apple products is pretty much illegal.
I have not heard of any country on this planet that has an explicit law that says "you are not allowed to install OS X on non-Apple hardware".
The worst thing that you legally do is that you violate the terms of Apple's End User License Agreement when you install OS X on non-Apple hardware. That is very far away from doing anything illegal -- at worst this is not respecting your end of a contract.
But this immediately leads to some other legal issues with Apple's EULA
1. Are the terms of Apple's EULA legal?
2. Can an EULA be legal and binding when you can only read it AFTER the purchase of the software?
3. And even if Apple gets away with it in the United States of America, what about the rest of the world that have more consumer friendly laws than the USA?
Microsoft found out in Germany and other countries that they could not bundle a software license to a specific computer -- people are free to re-sell pre-installed OEM/Systembuilder versions of Microsoft products in Germany. Microsoft's conditions were found illegal - they might make such a contract with a huge OEM, but NOT with an end-user. Now what makes anybody think that Apple's conditions would be legal?
Apple's Mac OS X product is sold for EUR 29 in a stand-alone box as a stand-alone product. If even has the label "RETAIL" on it in Germany - not upgrade, not update; it says RETAIL. And it does not say that you need a previous version of OS X in order to be eligible to purchase this box. (By the way: German courts have also ruled that you are allowed to sell the previous version of the software after you have purchased an upgrade. This is the reason why Microsoft no longer sells update/upgrade versions in Germany.)
So for EUR 29 I get an operating system that says in its hardware requirements "Intel Mac". Repeat: In the hardware requirements sections. Now that is the section that says something about technical requirements, not legal requirements. It's like saying "this set of wheels fits to an Opel Astra." Nobody could keep you from putting them on a Ford if they would fit.
Only in the EULA - which does not even accompany the OS X retail box in printed form - Apple mentions that you can only use this software on an Apple computer. Now, again, this is the point where such a condition in all likelihood is not legally binding because you only hear of that condition AFTER the purchase, that means AFTER you have concluded the sale contract with Apple. In the first three weeks of studying law at a university you already learn that something like this cannot be legal.
The worst thing that happens is that your contract with Apple is null and void and that you have to return the box to Apple for a full refund. End of story.
Still, the question remains if Apple --could-- enforce their EULA outside of the United States, and if they could be as successful against the German PearC company as they were successful against Psystar.
Apple's German Legal department hasn't moved against PearC, yet - and PearC is only selling their computers in Germany. I like to think that Apple already knows that their legal club is useless here, so they choose to ignore the little company that sells computers with an OS X Desktop Box Set.
I don't think that the question should be whether it is legal for the customer to install OS X on non-Apple hardware. The question is whether it is legal for a company to try to impose such conditions on their customers. And I think the answer has to be NO, this shall not be legal for any company.