Requirements

[craigpd]

You can download the free version which is just a multiplayer launcher, no singleplayer.

But to play DayZ you need to own Operation Arrowhead, which is in effect, an addon for Arma 2/ Arma 2 Free.

Operation Arrowhead works with the free version so you can save some money buy just buying OA instead of Combined Operations.

[Dutchmerc]

Rocket said that soon you wont be able to play with Arma II Free, it's best to buy Combined operations anyway

[bmanrules]

Well the only reason you need Arma II/Free is for Chernarus and the player models, so that shouldn't matter I don't think