The 5.0.x version of the adapter is only for the latest 5.0 version of Rails. If you need the adapter for an older version of Rails, just install the latest version of the adapter that matches your Rails version (3.2.x to 4.1.x).
Without channel prefix in Redis, apps using the same Redis server could have their communication compromised. You can now set the option channel_prefix in your cable.yml file. Please check the PR for details.