Synchronisation two boards

Hello community,

I need some help. Is it possible to have the same users on two different boards (two installations) without the same posts, attachments etc., only the same users - a type of synchronisation.

I think this should be possible with a bridge, or not?
Yes of course is this addon quite cheap, but as a pupil it isn't ^^

If I save some money, I will buy this Addon :)

Or I have to create my own bridge