Big media companies have fancy lawyers too, and if one of them expects to make a ton of money on the book, it will be published.
And there is nothing to prevent Donaghy, when he gets out of prison, from publishing it himself. Anyone can start a blog, and once the words are out there, it's too late for the NBA. In fact, it's probably too late already given what's up on the web now.
Maybe the NBA can strong arm ESPN and others to suppress the story, but it can't strong arm everyone, and if the NY Times or the Washington Post thinks Donaghy is credible, his story will be told.