Changing Forum software IS going to solve the Spamming issue. You just have to provide the somplest of all 'hacks' 'mods' or 'addons' to it. Something like Akismet checks every post if it contains spam (and this quite good. more than 99% of the time it is right). Other addons provide the option to check IP, email or username against a global database of spammers...
Of course you may want to check if this is possible with this forum, but i rather doubt it as we arent even using PHP (as it seems)..