I have it working on jessie now but had to do some extra tricks:
When adding the repository to the plugin page on the LMS server web interface i get the following error:
„Bad repository – Redirection limit exceeded“
This was fixed by installing the libio-socket-ssl-perl package
sudo apt-get update
sudo apt-get install libio-socket-ssl-perl
Perhaps you should include this package in the google music plugin installer.