As far as I know Arma 2:OA is on sale on steam, you could make a new account and just use DayZ Commander to launch the game from now on and use Darkys Key Changer to change your old banned key to the newly purchased one from your new steam account by simply copy and pasting it from right clicking the game in steam and going to the "view cd key" option. If one of your steam accounts is global banned every time you try to launch the game it will revert you to the banned key. You by no means have to use steam to play.