Well, it goes like this. A commercial product goes to sale, say people call it the iPhone. They have an SDK.
An enterprising publisher sees a legitimate opportunity for a book on the SDK. Publisher goes through all formal processes, or at least I guess so from the description provided, by signing NDA and all.
Now the hitch is the book is blocked, because the NDA is not lifted.
Are these guys serious?
[Update: Today, the 3rd October IST, I read that Apple have lifted their NDA. Good for them. The walls keep away innovation on their own platform. Without innovation, even Apple will turn out to be a commodity platform. And that cannot be good for the industry!]