What would BYU do if somebody else next year want to play on BYU's name? Every time somebody does that it weakens the brand and makes it harder for BYU to go after trademark infringers. Ideally, there was a licensing agreement in place and a nominal licensing fee paid to BYU so BYU can both show it's regulating its trademarks and maintain goodwill due to Retzlaff.
I was thinking about this when I saw that Dave Portnoy was making his own BYJew shirts. Hopefully BYU has already sent a stern letter to him for that.