QueenAlice said: "Universal owns the rights to the novel and the musical. There aren’t any legal issues."
That is commonly assumed - and as I stated, I have no actual information - but what Universal owns is defined by contract with Gregory Maguire. And if Maguire was reported able to sell a non-musical adaptation to ABC, then Universal does not own all rights to the book.
It would have been poor lawyering for Universal's attorneys (or whomever) to not negotiate obtaining the rights to adapt the book into a musical and any adaptation of the musical into another form (television, film, internet stream, ice show), but lawyers make mistakes. But, if there had been an issue, then litigation likely would have happened by now. As Buddy sings in City of Angels: "The book may be yours, baby, trust me, the movie is mine."