There are a lot of people who aren't happy about Steam's introduction of paid mods. Garry Newman, the creator of Garry's Mod, doesn't see a problem with the feature, though.

To get the Xbox 360's motion-tracking hardware to work with physics sandbox Source engine mod, you will need to pick up a copy of Garry's Mod, a Kinect and the Kinect for Windows Runtime v 1.6.