The thing (or the difference) between a book and this case is that for a book the author is *expecting* it to be read. However look at any teaching material, you are not allowed to copy or distribute it without having the author's permission. Here the code of the software is the key to their work. It's like you have a friend copying keys that had been provided by the possessor to make double of them. Would it be legal if that friend showed you how the key is made and that you later used this knowledge for other key maker in getting a genuine copy of the key without the original - just because your friend had let you look at it. In end effect it's not important where the leak is coming from, maybe it had been rightfully disclosed for a purpose, but using this purpose to get to another one without the knowledge of the possessor may get you in trouble. Like Apple - if a journalist come to release screenshots wherever they come before the software had been officially released, he will be sued and it's not going to help him to say he had not taken the screenshots himself. Screenshots that are publicy available are another matter, like publicy available books and undisclosed book content.
