The license was probably registered in your or your companies name. The license is issued per domain, but the owership of the license for that domain would need to be assigned to new owner. It's usually simple thing to do, but sometimes there is a small transfer fee.
Of I could be completely wrong...
Let me know if you hear from the author since I think I have the same script and would like to have that info as well. (Dragonscripts...right?), and hit me up when you get ready to sell....