How do you do that? I know some users can but I can not remember how it's done LOL
Anyone can if they have the address. Just send the required fee to the address mentioned. That's it. You have to do nothing else.
You already did your part by introducing them to this forum. If they are serious enough about crypto, they will pay the fees for unban. So leave this decision to them.
Not everyone knows about the forum. His friends thought it's scam forum which is asking for money for using the forum. I think it's good to let them get in the forum by paying little fees.