Is it considered exploitation to leave a non-Muslim worker to work in the place of a Muslim during Friday prayer, with his consent, and should he be compensated? And is that considered causing him to miss the prayer?

A Muslim must perform the prayers at their appointed times, in congregation. The obligation is even greater for the-Friday prayer, to which Allah has commanded us to hasten, and to leave off trade during it. Therefore, work or an employer cannot prevent an employee from attending the Friday prayer and congregational prayers. Prayer times are, by Shar'i exception, exempt from work duties, and an employer has no right to prevent an employee from them, even if this was not stipulated in the contract. If the work requires someone to be present during prayer time, then let someone who does not pray perform it. There is no injustice to a colleague in this, nor is it aiding them in disbelief; rather, they should be invited to Islam and rewarded for their cooperation.