Impulse is run by Stardock. Impulse is like Steam - a digital distributor and a client. Unlike Steam, you don't have to run Impulse client/program to run a game. This is good b/c you don't have to worry about forced to run Impulse and then maybe be stuck w/ additional 3rd party DRM.
You really only need to run Impulse program to actually get your updates or so you can "Archive" games, basically. Yeah - you can archive entire games like Steam and back them up on disc or anywhere else you want, as well.
Unfortunately - Impulse doesn't have Friend Tools and the Big Community that Steam has.