How do the rules of blitzball come to be? Which one of Finny's "Commandments" fits with blitzball?

Finny makes up a game called "blitzball," sort of a variation on rugby and football, and also adds new rules as they go.

"Finny never permitted himself to realize that when you won they lost" in terms of sports and other activities (27); he thinks that, as a rule, participating is victory, and doesn't believe in any other view on the subject.