It's download Tauren, never through to mention that.
Metatron, I have only bought one game from them which is Serious Sam HD when it was on offer, I already have Commandos on Steam. I'm not 100% sure on their DRM. It does use a non-standard installer though. Personally it's one game I would back up as soon as installed if I bought it. I think the installer downloads some game content, possibly... But once installed no connection is needed, there is no client or anything like Steam.
But hell at £2, it's worth a punt.