This is a bit offtopic, but if I give someone a gift code will they see my username and email address when they redeem it? I know they do if you send them gift to their email account.
Disclaimer: I've never redeemed any codes myself (that I can remember), so this is partly guessing.
To keep my e-mail account private, I gift games to my own e-mail account, and then I PM the recipient the code. As far as I know, there's no way to gift something completely anonymously.
It shouldn't be much of a problem for GOG to set up an anonymous mailing service for gifting (to existing GOG members), but I think you'll be able to see the gifter's GOG name regardless - someone please correct me if I'm wrong.