The project began last year as a mod for Arma 2 made by Dean Hall, who joined the Bohemia team when the studio announced in August 2012 that it would develop a stand-alone DayZ game. Bohemia originally planned to release a playable alpha by the end of the year, but the project suffered repeated delays amid other setbacks at the studio, including the detainment of two Bohemia developers in Greece.
Bohemia cautions that as with other Steam Early Access titles, DayZ is in a pre-release alpha state, so players should only buy in at this point if they want to contribute to the continuing development of the project — and if they're willing to deal with an unfinished game.
"Be aware that our Early Access offer is a representation of our core pillars, and the framework we have created around them. It is a work in progress and therefore contains a variety of bugs. We strongly advise you not to buy and play the game at this stage unless you clearly understand what Early Access means and are interested in participating in the ongoing development cycle," reads a description from Bohemia.
You can check out the DayZ alpha on Steam here, and watch the alpha launch trailer above.