Vault_Boy: To add some party knowledge, here's a shocking secret for all those Starcraft fans and DoW-haters: Starcraft was at first developed under the Warhammer 40K license but at some point GW backed out so Blizz all of a sudden had to come up with their own "ideas". Go figure.
Navagon: Aren't you thinking of the first Warcraft? Only I doubt that Blizzard and Games Workshop were in the same failed licensing situation twice.
From my understanding, it is one of those rumor/myth things that constantly get propagated.
The version I have heard (and that makes the most sense), is that Warcraft was originally supposed to be a Warhammer FB game. Something fell through at some point, Blizzard changed the IP enough, and released it.
Later on, Blizzard took a cue from GW and made a sci-fi version of their War* game, and Starcraft was born. It is up to you how much you consider it to be a ripoff, since Zerg=Tyranid=Bugs (from Starship Troopers) = Whatever, Space Marines = Space Marines = Space Marines = Space Marines (seriously :p), and Protoss = Eldar = Generic Fancy Elf-Douches with More Tech/magic Than Us.
But I don't think anyone who looks at the facts will disagree that Starcraft was inspired by 40k, to some degree.
But the thing to remember is: Pretty much until Relic got involved, most attempts at a Warhammer Strategy game kind of fell short. Don't get me wrong, Final Liberation and the like were fun games, but there is a reason that take on the genre is effectively dead in favor of the RTS. And Space Hulk was awesome, but a different genre :p
So while it is quite probable that Blizzard 'jacked GW, they have earned their IP and following.