My understanding generally concurs with swiv3d, although I believe (but may be wrong) that licence transfer is possible. I thought I read on the forum somewhere that you can reassign the licence details to a new email address by suitable request to the JRiver team.
That way when a licence restore is actioned, the automated process for sending out a new .mjr file will then go to the correct address.
Awooof77, if you don't get this when you perform a licence restore, then the "entrepreneur" you're referring to has sold you short.
If you go for a licence upgrade, the licence server will need to have your email on file. Otherwise, you'll be viewed as a new user and be subject to paying full price.
If I'm mistaken with the details, I'm sure that there'll be someone with better knowledge to clear up the finer points of how these things work.