Be helpful to get the views of an Admin or similar?…
I have seen forums like this split before, and they're never quite the same - you lose the years of topics and the reference material that makes forums so special.
I have been toying with the idea of approaching the admins to see if they'd consider handing the forum over, subject to it's running costs not being too mad. I work in IT, although I admit the phpBB would be a stretch for me. I'll mull it over. I think retaining the forum with it's topics is really important.