Cd key swapping???

my buddy doesnt play OA anymore and offered to give me his cd key. Would i be able to use darkys to change it and use his or would i get a cd key in use error?

If he isn't using it then no, you wont get the cd key in use error

You would be fine as long as he isn't on the key when your trying to use it. Could even swap back and forth between users and it would be fine.

3
isnt online at the same time or isnt installed on his pc?