This (will) page describes how to unclaim a Fedwiki site.
At the moment we have no idea :)
Indestructibility of Claims
Removing the site folder (status and pages), and clearing all browser data - achieves nothing. I can't find any cookies or other information being passed from the local server running on the laptop, and I've turned the internet connection off - still teh site is "claimed"!
#Fix by restarting server
The reason for this is that the Node server needs a restart in order to remove the name of the owner from it's memory.
The server reads the file when it starts, and holds onto the name of the owner. So, a wiki restart is needed so that the server starts and sees the site is not claimed.