Sounds very odd. You can't sell the script, you don't own it. You own the right to use it for a an environment where you yourself use it (regular license) or an environment for paying customers (extended license). Connected to one IP address.
@Charles - have a look at https://www.roboset.io/services/mailwizz-vps-install @OptiBiz1 - there are a few agencies that buy licenses in bulk, then they install those to various customers they have, and generally they search for a quick installer so they don't use much time when they get new customers. This may be the case as well.