Am I allowed to trade someone here for a game code I got on Humble Bundle? Or only GOG Games? I have an extra code, don't know what to do with it...

If it's allowed, anyone want to trade me for a copy of Vertiginous Golf?

Beware of scammers. Always check who you're really talking to.

these thread have list of known scammers aka BAD PEOPLE

If you DON'T FIND ANY POST OF THAT USER IN FORUM SEARCH THEN ASK HIM TO GIVE HIS KEYS FIRST

ALWAYS FEEL FREE TO REFUSE TO TRADE IF USER HAS NO RELEVANT POST

ask users with HIGH REP and OLD JOINING DATE about that user before doing trade

Feel free to contact me in case of any doubt :)

Also this is the trading thread where you can put your List of WANT and HAVE

Risky, very very risky.

Share it, maybe? https://www.youtube.com/watch?v=-qTIGg3I5y8

Write the code on several pieces of paper and bury them in random locations, then do a geocaching giveaway.

Wasn't there a wiki of known scammers?

http://www.gogwiki.com/wiki/Known_Scammers

Trading isn't officially sanctioned by GOG and thus isn't regulated by anybody except the community. The unofficial trading thread is here:
https://www.gog.com/forum/general/gogs_general_trading_thread
However, BEWARE OF SCAMMERS. There are some nasty people on this thread who prey on folks like you and try to convince you to give up your key without giving you anything in return. Always check the list of known scammers that the guy above me posted before trading, even if the person seems to have a high rep number. If in doubt, you can ask for a list of people they've previously traded with, or ask me and others to check them out for you. Myself, Sachys, amrit9037, toxicTom, tinyE, and Hypersomniaclive are people in particular who I know can assist you in this.

If you just want to dump games, please PM the host of this thread for GOG games:
https://www.gog.com/forum/general/the_community_giveaway/page1
and this thread for all other games:
https://www.gog.com/forum/general/the_community_giveaway_steam_edition/page1
Give either one of them your code, and they'll make sure it goes to a good home. If you frequent the community and become an active member, you can ask for games from either of those threads as well.

Now, on a more personal level, I can't quite tell whether you're saying you have a copy of Vertiginous Golf to trade, or you want to trade to get a copy of Vertiginous Golf for yourself. If it's the former, I have, like, 3 of them already, so no thanks. If it's the latter, I have, like, 3 of them, and you can totally have one for free.

You can, but Gog won't protect you in case of troubles.
Also, a scammer is infesting the forum since months, stealing many games.
It's risky because he can easily create fake alt accounts (also impersonating other users) and alter both his own and other users' rep.

And another one scared off...