I actually own a license for IP.Board and IP.Downloads. If I want to give these licenses to someone else, what do I have to do? It's not an offer to anyone, just to know what to do if I want to give my licenses to anyone else.

I dont think you can sell or give your licenses away anymore , but ill leave it for staff to say

Actually I don't want to sell/give anything, I just want to know how it works if someone wants to give or sell a license for an IPS product. :)

you have to give up your whole account

You have to turn over your entire account to the new account holder. Of course you are encouraged to remove any credit card details or other private data before doing so.