I doubt that the website is using the same website to process their plimus payments. Doing a google search does suggest that Plimus may be involved with their payments though. Maybe someone could do some undercover work to get the contractId that they're using.

Plimus does not support piracy. We have tens of thousands of registered vendors and it is extremely difficult to monitor the ongoing business activities of each and every vendor. We are therefore also reliant on peer reporting by users and program owners to bring potential piracy issues to our attention for investigation.
Our standard terms and conditions for Plimus sellers provides the following:
f) WARRANTY OF TITLE AND USE.
1. The Vendor warrants that it (and anybody authorized by it) has the right to distribute and license the Product, that such distribution and sale is lawful, and will not infringe the intellectual property rights, or any rights, of any third party, and further that no fraudulent or unlawful use of the PlimWare software and services will be caused or permitted by the Vendor.
 
Derek, Plimus