Activating License

Hi I have the Catch Fullscreen Pro and note that with version 2.2 it will update automatically with License code. My understanding is that having purchased the theme I can use it on any number of websites (which I do, because it's good!) but having activated the license on one site it will not activate on any others. Does it only activate on the one site or is there a glitch in the system? As I can use it on any number of websites I would have thought it can be activated on them all. Maybe I have misunderstood something. Thanks, Chris