This was sent in to Robert's site ..... be sure to attribute it accurately if you are using it in any way.
As far as I know these "Rules" were the work of Corita Kent , (1918-1986), serigrapher and teacher extraordinare, in which she included a quote from John Cage. The calligrapher David Mekelburg produced them in hand-carved stamped lettering and they were published in Learning by Heart: Teachings to Free the Creative Spirit , a book begun by Corita with her former student Jan Steward and finished by Steward after Corita's death. (Bantam 1992).
(RG note) Thanks, Trish. We stand corrected and I definitely want to give the correct attribution. It seems Rule 10 is Cage's.