Linking GOG and Steam at the same time.

This account has a FAF link from Steam, and I accidentally linked my account with GOG, and I wanted to make this link to a friend, how can I unlink my GOG account?
The game was bought on steam and on GOG, but I don’t need a link to gog.

You can't unlink an account.

"Nerds have a really complicated relationship with change: Change is awesome when WE'RE the ones doing it. As soon as change is coming from outside of us it becomes untrustworthy and it threatens what we think of is the familiar."
– Benno Rice

These kinds of software licenses are often non-transferrable meaning that if you buy the game for yourself, technically you shouldn't be letting other people play your copy.

Is that a silly rule? Maybe. But the whole point of having Steam-linking and GOG-linking is to protect FAF from being accused of facilitating copyright violations.

I have some good news, though: "Supreme Commander: Forged Alliance" is on sale NOW at Steam for just $2.59

So if your friend has a Steam account, he can buy the game for himself for just $2.59

The offer ends in 20 hours, so: act fast