Export all jambook tables from the old install with phpMyAdmin or similar tool and import them into the 1.5. Then install the same version of Jambook as in the 1.0 install. Done
At least I think that's how I did it. I may have had to install in 1.5 first, then drop the jambook tables before importing the old ones. I moved several extensions this way, including Jobline. As long as the database character set and collation are the same and the table structure is the same, this works just fine.