As mentioned in the steps above any new user who tries to log into the portal gets automatically added to the portal. Below are few of my questions.
Test Data Manager
TDM Web Portal
Answers to your questions:
1. I am assuming this is a functionality of the Portal for AD group/role-based access.
But can we disable this feature to prevent users from getting automatically added?
This is the designed function. No, it cannot be disabled.
2. What are the license implication?
None at this time.
3. We have a license for I think 20-25 named users.
Will a user added to the portal but doesn't have access to any tile/functionality from the portal count towards the license use?
Yes until the users log off.
HOWEVER, if more than 25 concurrent users is exceeded.
(no degradation or denial of service happens.)