You can set several protection keys or login/pass combinations in capmonster protection settings.
This will allows you to give individual keys for users and track who is using software.
simple no.
long way yes. but its involving a "middle man" where you can setup keys and send get jobs from capmonster than to your client.
so client will send to your middle man the job than middle man send to capmonster and so on.
middle man can be a php script for example with a small db or no is up to you.