Posted June 09, 2017
If you have something in your steam inventory, then you can send it to the other persons steam account. You can keep the GOG key to trade unless you use it.
XyleDaylight: Can I trade games that are in my steam inventory for gog keys? If I get a gog key, do have to activate it or can I keep that around in case I want to trade it again later?
To check if the GOG key works, go here and put the code in, and redeem it. Then, when the game comes up, it will tell you what it is, and when it expires. From there, you can click cancel to stop the redeem code, or continue (I think) to add it to your GOG library. Please note, if you are wanting to trade a code on that you got from someone else, it may have their username on it.