Guys, I have to say I think some are being a bit unreasonable.
His intentions are clearly good and he's not attempting to gain unauthorised access to content - he's asked a simple question.
Makaze, I am not familiar with the user notes add-on, but I would be surprised if it wasn't possible to write a query that could import the data from vBulletin user notes to this add-on.
After all, if an importer can be written to migrate a whole board, I'm certain this task should be easy.
Obviously to get practical advice on how to achieve this, we can only help licensed customers, but to answer your query, yes, I would guess that it should be possible (but can't be certain).