I don't think it is as easy as using some import software. You most likely don't have another choice than writing a shell script to import other and corrupted databases, even e.g. for merging old posts with current user IDs you need some kind of mapping to correctly identify users from different databases to have a proper connection between them. That's quite some work, I unfortunately also had to do a couple of times and the most quickest way was always to directly write it on your own. Once it is correctly imported into one of the major forums db it can be easily converted into anything.