No, ListMessenger Pro can only be installed on one website/domain per licence key, as clearly stated in the terms of service that you agree to when purchasing and installing ListMessenger.
You may; however, post ListMessenger's end-user forms on as many websites as you desire as long as they all lead back to the single instance of ListMessenger you have installed.
If you are caught with an illegal version of ListMessenger, unfortunately your key will be black listed and you will not be able to use your copy of ListMessenger. If this happens you can purchase a new key one time; however, if you're caught a second time your account will be banned from our key system.
If you intend on purchasing more than 2 licences of ListMessenger Pro, please contact firstname.lastname@example.org to arrange a reseller agreement where you can receive and additional $10.00 CAD off of the retail cost of a ListMessenger licence key.