Well, you're not infringing anyone's copyright. You're not claiming someone's intellectual property as yours. You're not profiting from someone else's creation. It's not like you're watermarking a picture that's not even yours.
You're just sharing something that the developer/distributor is already sharing, in the form of a beta copy of the game. You don't have to worry about anything.
That being said, thank you for the heads up, my man. This is a tower defense game, if I understand correctly?