Linux is not in the public domain. Linux is a cancer that attaches itself in an intellectual property sense to everything it touches. That's the way that the license works.
Bio: Sir John Pratt was an English judge and politician. He was Lord Chief Justice of England from 15 May 1718 until 2 March 1725. He was appointed as an interim Chancellor of the Exchequer on 2 February 1721 until 3 April 1721.