As it's (seemingly) based on phpBB, you don't need to convert it - just strip down the database with the cleaning script
mentioned here in the forums and in the KB. Ofcourse, do a full database backup first and check that the structure is the same.
OK, I was completely wrong about that. It runs it's own database system, and there's even a phpbb -> fsb convertor - you might want to take a look at that to do it 'backwards'.