What is the ruling on affiliate marketing for a company that does not own the product, but rather displays the products of their owners and undertakes to deliver them to the buyer in exchange for a commission for the company and the marketer?

The fact that a company does not own the commodity does not mean that its sales are forbidden; it may be acting as an agent for the owner, or selling it through a forward sale contract (salam), or through two separate contracts (parallel salam).

If the transaction is permissible, then there is no objection to marketing it and taking a commission.