Downgrading vB4 to 3.X?

Hi everyone!
I am planning to convert my vBulletin 4 forum to Woltlab's Burning Board (they're a little less known but make a really nice forum software). But the way it looks they (and pretty much any other software I looked at) don't offer converters/importers for vBulletin 4.
XenForo and IPB are not an option for me (although I like both better than WBB, but it's a cost thing).

So my only option is a really dirty one. Downgrade to vB 3.8 (although that is kind of an upgrade lol) and then convert to WBB.
Does anyone know of a script that will do that? I would really like to keep all attachments and that kind of thing intact.

 

If Woltlab would not offer an importer for vbulletin 4 then that would make me think about how serious this company really is. Woltlab is in direct competition with vbulletin and with vbulletins current state, they would have to be out of their mind if they do not add an importer after Burning Board 4 is released.
Its to be expected that all hands are on BB4 now and therefore there is no importer yet.
I cant imagine that they want to refuse many thousands of vbulletin customers. If they do then there is something very wrong.
I would forget about downgrading to vb3.