Forum Moderators: not2easy
Regards!
As for copying the structure of your forums, welcome to the club. It happens alot unfortunately. Unfortunately there is not alot that you can do about it unless you can prove that your are suffering a loss of some sort because of their actions.
However you can contact their hosting company and tell them about the issue. Most web hosts will shut down sites that do something like this because they fear lawsuits or complaints.