Yes it will work. I used in back in December to activate my MobileMe. Bought old .Mac 5.0 off eBay and used it to extend my 60 day trial for another year. Unless Apple disabled all previous .Mac codes which I highly doubt they have, it will still work.
If he is a friend, can you not ask him if you can use the code and providing it works you will pay? If it does not work he would not be out anyway because it is not lie he could have sold it anywhere else. At least if you try it and it works then you pay.