Technically he doesn't have; but the whole GNU work would be worth of 10 PhDs and I bet many people did their own PhDs on top of work he did. If he was awared 1

Technically he doesn't have; but the whole GNU work would be worth of 10 PhDs and I bet many people did their own PhDs on top of work he did. If he was awared 1 or more honorary doctorates (implying the person is a doctor honoris causa), it might be acceptable to call himself a doctor, but not a PhD, which he didn't.