Interesting, however the OS X Terms of Use specifically restrict the OS to being run on Apple Branded Hardware,
So unless you are running Linux on a Mac and then virtualized OS X in that, running OS X on non-Apple hardware either natively or virtualized is against the Terms of Use.
2. Permitted License Uses and Restrictions.
A. Preinstalled and Single-Copy Apple Software License. Subject to the terms and conditions of this License, unless you obtained the Apple Software from the Mac App Store or under a volume license, maintenance or other written agreement from Apple, you are granted a limited, non-exclusive license to install, use and run one (1) copy of the Apple Software on a single Apple-branded computer at any one time. For example, these single-copy license terms apply to you if you obtained the Apple Software preinstalled on Apple-branded hardware.
B. Mac App Store License. If you obtained a license for the Apple Software from the Mac App Store, then subject to the terms and conditions of this License and as permitted by the Mac App Store Usage Rules set forth in the App Store Terms and Conditions (http://www.apple.com/legal/itunes/ww/) (“Usage Rules”), you are granted a limited, non-transferable, non-exclusive license:
and a bit later
(iii) to install, use and run up to two (2) additional copies or instances of the Apple Software within virtual operating system environments on each Mac Computer you own or control that is already running the Apple Software, for purposes of: (a) software development; (b) testing during software development; (c) using OS X Server; or (d) personal, non-commercial use.
This has always been the way that Apple has been, except for that brief time they allowed 3rd party hardare to license Apple OS's, Apple software only runs on Apple hardware.
So if you know of another EULA that permits this I'd lovve to hear about it.
regards