Do you have to use BulletStorm in order to play the Gears of War Beta?

I bought the game for the Gears of War 3 beta key but figured I'd beat Bulletstorm before selling it for achievements and what not. On the main menu screen though, I see that there's a selection at the bottom that says something about Gears of War 3 Beta. Do I have to keep the game in order to get into the beta or, since I activated the code that came with it, can I sell it off and still play the beta when it comes out? I hope so because not too interested in keeping the game after I beat it. Thanks for help in advance and take care.