>If there's an internet connection you could roll your own. Could be easy to implement using SignalR - each usage to keep a 'heart-beat' with the server which would then only allow xxx connections at any one time. Of course that would mean that the assembly could be installed on more machines than were allowed - but if the total number in use at any one time is controlled then that may be a good thing ?

I will do some research on that.

Thanks