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The mere fact that Apple claims that creating a hackintosh violates the DMCA, and that their EULA is an enfoceable contract, does not make either so. There are rulings in their favor from the Psystar case, but it is not clear whether those rulings apply to end-users or only to companies like Psystar who were reselling hackintoshes.
The chance of an individual being sued is essentially zero, because Apple doesn't want the bad PR of exposing their morally repugnant, monopolistic, anti-consumer tactics to the public any more than necessary.
It is my (totally non-authoritative paralegal-school dropout) opinion that even if Apple's EULA were ruled enforceable, the clause forbidding use on non-Apple hardware is clearly a tying agreement in violation of the Clayton anti-trust act of 1914, and so would be thrown out.
Google gives the following definition of "illegal":
contrary to or forbidden by law, especially criminal law
However, your friend appears to have only committed copyright infringement, and possibly breach of contract if you believe that end user license agreements are enforceable contracts and that he formed a contract with Apple by using its operating system.
I am not a lawyer, but I think that in most countries breach of contract and small-scale non-commercial copyright infringement are civil wrongs rather than crimes, so perhaps "illegal" is not the right word to describe your friend's use of a hackintosh.
How about the Apple OSX License Agreement:
http://images.apple.com/legal/sla/docs/OSX10103.pdf
in particular, Part 2, section I:
I. Other Use Restrictions. The grants set forth in this License do not permit you to, and you agree not to, install, use or run the Apple Software on any non-Apple-branded computer, or to enable others to do so. Except as otherwise permitted by the terms of this License or otherwise licensed by Apple: (i) only one user may use the Apple Software at a time, and (ii) you may not make the Apple Software available over a network where it could be run or used by multiple computers at the same time. You may not rent, lease, lend, sell, redistribute or sublicense the Apple Software.
The License earlier says how you may obtain a license to the software, which is basically: buy a Mac, buy OSX in App Store, or get a volume license. In any case, none of these grant running OSX on anything other than Apple Hardware. You can run it in a VM, but only on a VM hosted on Apple Hardware.