"It’s a game much more involved than chess, a game where you can make up your own rules and where the end result is whatever you can make of it."

The rules and end result of a game of chess are clear-cut. What is he talking about? It's true that someone has previously decided on the arbitrary rules of chess, but UNIX also had been previously defined before Torvalds re-implemented it, and there are other ways to design an OS.