Questions about Demigod and the Stardock store

When I buy Demigod from the Stardock store, do I get an installer to download, or just a steam key?

Also people on steam are saying they need to register the game with Stardock.  Is that just for multiplayer or do I need to register for singleplayer against the bots?

Is there a DRM-free option to buy this game?  Are you going to release Demigod on GOG like your other games?

Thanks.