Assuming he never paid any money, there are times when they have free games and you claim a game you already got you get a gift code (
Though it seems some expire but don't say when they do in your order list...) So if he had one that hasn't expired he certainly could give you said code.
But overlapping game codes i've seen is rather rare.
Timboli: My understanding, is that you have to have spent at least $10 at GOG, but not necessarily in the last 3 months., you just have to have been a member for at least that long.
Primarily to battle stolen credit cards and buying gift games to sell elsewhere before said funds are revoked. I'm not sure if 3 month membership or 3 months after making $10 worth of purchases in order to see if there's flags to said payment methods as they would happen within that time probably.
But either way it's not '
you have to purchase within 3 months to be able to gift'. That would be annoying, especially if a good sale came up and you had games you already owned but couldn't buy gift codes because you hadn't purchased anything recently.
Regardless MJSTXplorer, do you know what games he would be gifting you? It's possible others have expiring codes or are willing to trade said games they already have.