OMGeek to Deploy ARMA 2 Server Soon!
It's recommended you have ARMA 2: Combined Operations (ARMA 2 + Operation Arrowhead) to enjoy the game to the fullest. At the very least please have Operation Arrowhead, although I'm not sure yet if downloadable maps are backwards compatible. I will update this thread once I get more information.
If you don't have ARMA 2 also, you may download the free to play version. Think of it as the lite version of the game, as it still lets you play online, but without the high res textures or user mods. So there's no excuse for you guys not to come try it with us.
I've been personally been wanting an ARMA 2 server for the longest time and can't wait to get into the thick of it with my fellow OMGeeks!