Is it permissible for my husband to take money from his grandfather, who deals in usury, and then use it to buy food for the birds he raises and sells, or to repair his car, knowing that my husband does not use this money for his own food or expenses?

It is forbidden to engage in usurious transactions, whether lending or borrowing. This includes investment deposits in riba-based banks. Whoever engages in usury must repent, cease the practice, and dispose of the usurious interest by giving it to the poor and needy or spending it on public welfare. It is not permissible for him to benefit from it, unless he was ignorant of its prohibition. Giving prohibited interest to the poor is permissible and good for them, and they are allowed to take it.