Is taking a commission from a European factory—which is presumed to deal with usury—lawful or unlawful?

It is permissible to engage in transactions with non-Muslims and to receive commission from them in lawful trade. There is no obligation to investigate the source of the funds from which they pay the commission, unless it is definitively known that their wealth is illicit. It is not permissible for a Muslim to sell weapons or instruments of war to the people of war, or anything that aids them in establishing their religion, nor to sell a copy of the Qur'an, nor a Muslim slave to a non-believer under any circumstances.