I should mention that I own three original OS X licences/CD sets (one that came with my iBook, one that came with my G4 iMac, and one boxed retail copy that I bought from the Apple Centre Manchester).
When I bought it I was not asked if I owned a Mac, I was not asked if I would be running it on a Mac, they were quite happy to let me pay my £100 and walk out of the store with OS X.