To move a license key from Site A to Site B without any problems, simply verify the license key on Site B on the Quform → Settings page. The license key will now be associated with Site B. Site A will become unlicensed after a short amount of time.
If you have an unlicensed copy on a development or test site, you can still continue to use it, the unlicensed version has all of the functionality of the licensed version, excluding help and automatic updates. It is no problem for us for you to test or develop with an unlicensed copy.