Do you have any protection method if the customer disputes the payment after activation?
ElecKey Internet/Ultimate PLUS includes the automatic license validation feature. If, for example, you get a charge back from the provider, you would login to Activation Manager and enable the Destroyed license for such a user account. Each time the user runs your application, it will connect to the server to validate the license. Now that such account is marked with Destroyed, the application will automatically delete the license from the user machine.