What is the ruling on dealing with a broker who brings customers to an online store, if the store owner knows that the broker is a bank employee who uses credit cards of deceased individuals who have no heirs to complete purchase transactions?

There is no objection to dealing with a broker for a known commission for each client he brings, but if you know or strongly suspect that he is purchasing programs with the funds of deceased cardholders, then it is impermissible to deal with him. If it is merely a suspicion, the transaction is not forbidden, but it is disliked as a precaution against doubt. If a person buys from someone whose money is a mix of lawful and unlawful, then if it is known that the sold item comes from his lawful wealth, it is lawful. If it is known to be from his unlawful wealth, it is unlawful. If it is not known from which of the two it comes, it is disliked due to the possibility of unlawfulness, but the sale is not invalidated because lawfulness is possible.