Funny, i've spoken to others who have done this change and they paid.
All the mods cite this as well.
According to the posted rules..
8. Please do not register more than one chat nickname.
Registering multiple usernames is prohibited. Each person should have only one single identity in the chat rooms and the forums. Also if you want to change your username, understand that we have to delete your current account and let you register a new one (so you'll lose all data, though any forum posts will remain with the old username but with usertitle "Guest"). If you're not already a supporter of the site, we charge a $5 fee for such requests.
Perhaps, Sib, you fall under this banner? "If you're not already a supporter of the site, we charge a $5 fee for such requests."