I'm happy to announce that Authlib got its first sponsor Auth0.com. Thanks Auth0 for sponsoring Authlib.
Auth0 has sponsored many open source projects, including my previous Flask-OAuthlib. I'm happy to take it as a sponsor for Authlib. I do encourage you to have a try on their service, it is quite easy and in most case it is free. I find it quite useful for single page application.
Here is a total free use case. Consider that you have some single page applications that only allows your company members to access. You don't have to create a server for it, just use Auth0.com, and embed it in your SPA, no one piece of backend code for authentication. You can use a simple domain whitelist to allow ONLY your company members to access the SPA. Your company members won't exceed 7,000 free active users, right?