Aren't the "upgrade" versions considered OEM? Meaning, once they ship, they won't be in a "retail" box, but perhaps a white box or just a DVD sleeve? (perhaps I'm referring to the "free" upgrade to 7 discs when you buy Vista)
Personally, I wouldn't even trip, as you can see plenty of "questionable" for-sale Windows products on Ebay as it is. Besides, you haven't installed them yet, so should be able to do as you please with them. OEM software is stamped indicating that it's to be distributed with a new system and not for re-sale, but I've bought them from people in the past (and they were brand new, still sealed).