Recruit-a-Friend question

I have a friend interested in doing the RaF link to my account. The issue is is that he already owns (paid for) vanilla WoW and Burning Crusade expansion on his computer. Will he have to purchase new games of those 2 again or will it still work with his current copies?

To clarify, he has entered their activation codes, but has not actually played on the game with a real account (only trials every so often).