Using Mendix as only REST API and implementing frontend in modern web frameworks

I would like to know how we can use Mendix as just REST API server, and implement frontend in any of the modern web frameworks. All the communication btw client and server will be JSON responses. I know how to expose database entities through REST resources, major doubts are around: How licensing works for this use case? How to handle users authentication & authorization? (like use JWTs?) How to handle user roles? I know Mendix provides all of these by default if we use Mendix for frontend too, but I want to explore this use case.