What is the ruling on participating in a business venture with those who have taken out usurious loans from banks in their personal names, and not in the name of the company?

It is not permissible to partner with people who have entered a company with money they borrowed through usury, because that involves introducing forbidden money into the company and assisting them in sin and transgression. However, if they entered the company with lawful money, and they have usurious dealings outside the scope of the company, then there is no harm in partnering with them, though it is more prudent to avoid that.