Is it permissible to take a fee (dues) for giving computer courses on devices dedicated to Allah (waqf), to cover maintenance costs and the teacher's salary, and to ensure students' commitment, given that not using the devices would harm them?

It is permissible to charge a fee for courses equivalent to the expenses necessary for device maintenance, even if they are endowed (waqf). If the purpose of the endower cannot be achieved except by paying fees to instructors, then it is permissible to increase the fee to include maintenance and instructor salaries. The waqf should be maintained from its revenue. If it has no revenue, then a portion of it may be rented out to cover its needs, because spending on it is essential for its preservation. As for the lack of commitment of some students in free courses, this is not a valid consideration for charging a fee; rather, the consideration is the need for maintenance or instructor salaries.