Both the company that wrote the algorithm that submitted the request and the company that responded by creating a listing.
“What responsibility do print-on-demand providers have to prevent infringement on their platforms?”
All of it. The company that submitted the request also has all of the responsibility. It doesn’t have to be split between them. They are both 100% responsible.
Who’s responsible for this infringement?”
Both the company that wrote the algorithm that submitted the request and the company that responded by creating a listing.
“What responsibility do print-on-demand providers have to prevent infringement on their platforms?”
All of it. The company that submitted the request also has all of the responsibility. It doesn’t have to be split between them. They are both 100% responsible.
(Disclaimer: IANAL)