G17 Media's post in Protect license key verification was marked as the answer
I think there was some talk about IPS not permitting encoded files on the Marketplace but I could be wrong. As for IPS, there is a hardcoded license check. It can be removed by commenting it out, and there are numerous sites that offer pirated versions. Like a lot of PHP projects, they mostly work on ordinary users not knowing how to remove the license check, copyright enforcement and the honour system.