Question About Space Farmers

I bought Space Farmers at Daily Indie Game just now and activated it, putting a copy in my library and one in my inventory to gift. I BTA on this though, so I have a second Steam key for another double-pack of the game. While I can just give away that second Steam key, what will happen if I try to activate it myself? Do I get 1 or 2 copies in my inventory? Or will it not activate since I already have the game? If anyone knows, please let me know. Thanks for your help!