Seems this site has been reported to XF a lot, there's no license clause they can invoke and they do not have a valid license. So someone needs to find their host or where there servers are and go that route.
idk what you can do to help. but this site is someone that runs your software. their site has been shut down 4 times. and they keep poping up. is there someway you can revoke their service they have with you does it break TOS?. they have been sharing CP aka illegal pictures. and openly condone...
xenforo.com