Do I need to keep Impulse client after downloading a game?

[fullmetal]

I see that Chivalry is on sale at Gamestop right now, and I missed out on the Steam sale a few weeks back. I'd like to get it, but Gamestop says I need their client to download the game.

Since Steam is required, once I've downloaded the game and activated on Steam, do I need to keep the Gamestop client installed on my computer?

Any help is appreciated.