I believe it was 5 sessions at some point.
However this can easily be double checked when constantly logging new users to the system via /login.html
You will quickly run into this hard-stop. Also an anonymous user counts as a user in the system and towards the trial limit.
As it was said, I believe the limit is five, we had an situation where we needed to use multiple instances and sessions, and when we hitted 6 sessions, it stopped working correctly.
how to increase the number of sessions?