It seems like I was wrong:-
In "man-in-the-middle" mode (see command-line argument cirrus in usage part) you must indacted on side flash your Cirrus key developer.
_netConnection.connect("rtmfp://localhost/KEY");
Of course "KEY" must be replaced by your Cirrus development key.
It requires the Cirrus Development key only when used in - "man-in-the-middle" mode.
Otherwise, I assume that there are unlimited connections possible and not limited by what adobe offers - max 10k concurrent users to be using the free service hosted by adobe.
Correct me if I'm wrong again!
Best
Rajan