Thanks for sharing this project, looks very interesting.
Does it allow for fallback, ie if you are not authenticated via Gapps, can you login with a standard Alfresco account?
The users created, is the user id equals to email?
Is there a way to turn off auto-creation and only allow for pre-created users to login?
Another thing is if one could map existing user id:s to Gapps user ids.
Haven't had the chance to test your add-on, but will do when I find some time.