It's against the EULA, but in general, each provision of a EULA is treated separately (at least, according to Wikipedia), i.e. so a part of a EULA might be found to be legally non-binding. The legality depends on where you are, but if you're in the US, I would guess it's illegal because of the DMCA. Apple sued a clone manufacturer(Psystar) several years ago for selling machines with OS X installed on them. They sued under several different legal reasons, but one of them was that Apple uses encryption methods protected under the DMCA to keep OS X from being installed on non-Apple hardware. The court found that indeed the DMCA was violated and Apple won.