an importer would be needed which we dont currently have. Moving the forums, topics and responses would be fairly straightforward (look at the db structures).

the harder issue would be getting the users and associated data over to wp since they have their own user database.

On an integrated BBpress setup, it would be easier as they can interlink databases and the user and usermeta tables.

I was researching bbpress when I first stumbled upon Simple Forum, before the name change, way back in version 2.1

Even back then Simple Press Forums knocked the doors off BBpress.