Is there a sin upon the agent of "Gold Star" company, owned by Ahmed Bahgat, who is also the owner of Dream TV channels?

If the company does not sell prohibited items, there is no objection to your friend's husband acting as its agent, even if the principal engages in other forbidden activities. The general rule in transactions is permissibility, and the Prophet, peace and blessings be upon him, engaged in dealings with Jews. However, if the company involves prohibited transactions, it is not permissible to deal with it through agency, buying, or selling, because that would be cooperation in sin and aggression.