Dean Hall’s DayZ modification for Bohemia Interactive’s Arma II has become an officially offering as it gets added to the Steam store page for the military simulator. This is not the standalone release.
The DayZ Mod is available freely with a clear warning that it ”requires Arma II: Combined Operations” to be installed, and that the original game and Operation Arrowhead must be run first.
Bohemia and DayZ’s creator continue to work a a full standalone release for the zombie survivor sim. Check out Steam’s DayZ Mod page for more information.