Is it permissible for students of knowledge, who already receive stipends from a first sponsor, to accept stipends from a second sponsor?

Supporting those who teach people is among the best acts of devotion, and giving charity to them is more deserving. There is no objection to the teacher receiving salaries from supporters, provided that the supporter does not stipulate anything that would negate the teacher's entitlement, such as stipulating that the teacher should not have another supporter, or stipulating that the teacher must be needy and therefore should only take what suffices their need. The condition set by the donor is to be honored.