You should read about Monster Cables and how they go after ANYTHING with the word "Monster" in it. They were dumb enough to go after Disney for Monsters Inc and discovered they bit off more than they could chew...
Games Workshop isn't known for being all to nice anyhow. While working in the industry full time I had RPG shop owners tell me how, once they started selling a lot of GW stuff, GW would open a store near them then cut them off. Never got any first-hand verification of this, but I had three store owners that didn't know each other (not even in the same states) tell me the same thing.