Your license for GExtension is a string with numbers and characters. It's valid for one IP (webserver). Your license will be automaticly devaluated if you get permanently banned at GmodStore or when your purchase gets revoked.
Feel free to create a support ticket if you have any problems with your license.
Transfer to new webhost
It's easy to transfer your GExtension installation to a new webhost. Just copy the files to the new webhost and make sure that your MySQL connection works correctly. Upon opening GExtension in your webbrowser, you will see a notice that the license is invalid or has been used with an other IP-Address. Just follow the URL in this notice. Click on the red "License" button. Now click on the "Retrieve" button and reenter your license in the given field. Submit the form and GExtension is now activated again.