This is a Plex channel for Google Music.
Since the plug-in contains binary code you have to download the right version for the platform that your Plex server runs on. Then read the docs on how to install plug-ins manually.
Once installed you must enter your username and password into the channel's preferences. If you use two-factor authentication with your Google account you must create an application password.
This software is licensed under the Apache License Version 2. See LICENSE for details.