One forum running on the site that was imported from previous software on the same domain.
Second forum on different domain. Can it be imported on top of the current forum?
I don't know if it can happen or not. Users would be merged by email. Would not check keep the same id's since there are already posts in there. Keep the archive log table in the database. Assuming it would create all the forums from importing forum so would have to do some queries to place all of those threads into the appropriate forum. Place the redirect htaccess on the other domain and then the redirect files on the 1st server.