At the moment is not possible to reopen the authentication popup.
Kerbynet is the the interpreter of the templates you can find in the directory /root/kerbynet.cgi/templates. The templates (HTML and Javascripts) and the bash scripts in the directory /root/kerbynet.cgi/scripts can be modified, but instead the kerbynet binary ad moment cannot. This is because I will have to decide for the first stable release if it will be released (the kerbynet binary) using the GPL or not.
Regards
Fulvio