Steamworks

[sillytuna]

From Valve: http://www.steamgames.com/steamworks/

Save months of development time and eliminate technology licensing fees. Plus, all of the features of Steamworks can be used alone or in combination with each other or your own existing solution.

Steamworks is not engine specific and will work with any underlying technology. Whether you're publishing your games on Steam or not, Steamworks lets you take advantage of Steam features in retail products.