Do I always need a separate license for a secondary server running the control daemon?
And if I have an unlimited license on my main server, do I still need an additional license for my secondary server running the control daemon?
And how does the number of stations work, when you have a main server and secondary server?
Thanks!

As far as I remember you only need new licence for control panel not for control daemon.

You simply install and configure daemon on your server to talk to control panel on another server.

Daemon servers also require their own separate license