E10 relies upon an in-memory cache for list of sessions and license ‘reservations’. You can call the AdminSession API for this information.
And since it’s me - I use the REST API:
https://MyServer/ERP10/api/v1/Ice.BO.AdminSessionSvc/List
To get the User and Session type, pop this into a browser once REST is setup:
https://MyServer/ERP10/api/v1/Ice.BO.AdminSessionSvc/List?%24select=UserName%2C%20SessionTypeDescription