Is it permissible to use donation funds to guarantee micro-entrepreneurs in repaying profits and defaulted amounts on their loans, and does the ruling differ if the financing bank is usurious?

It is necessary to observe the conditions set by the donors regarding the areas of expenditure, as the institution acts as their agent, and an agent may only act within what they have been explicitly or customarily authorized to do.

As for the issue of the institution bearing the profits on behalf of project owners due to loans:

1. If the loans are interest-based (riba), then it is not permissible to assist in them by bearing the interest, nor is it permissible to spend donors' funds on that. Bearing the interest does not change the fact that the loan is usurious and forbidden.

2. If the transaction is a legitimate financing, then there is no objection to bearing its profits on behalf of the project owner, provided the donors permit it.

Striving to do good and help those in need is a commendable objective.