Question 'bout keys.

Store.bistudio.com ain' selling STEAM keys no more. I was thinking, what if I buy a operation arrowhead key and use cdkey change ron the steam copy, will that work?

Yes, it will as long as you never launch it through steam ever again (Change settings in DayZ commander etc)

I just tried a key from keydirecthouse and it doesnt work.
What should I use to launch it? DayZ commander? or the .bat in their folder.

if they supply you with a .bat, then use that.