Extreme Networks EXOS ConfigSource

Have you tried writing the configsource yourself? If you know the commands required to display the config after logging into the device via SSH, it should take too much. Similar to this or this, just substitute the command(s) to execute. For configsources, all you need to do is have your script fetch the config (however you want to do that), then print the config to the screen. Your config checks then take care of alerting on the circumstances you define.