Imagine you want to buy a bearing-producing machine. You come to the most reliable seller (let's say his name is Mr Gregory Bapple) that there is in your whereabouts and tell him you want to get a consignment of those machines.
Once you unpack the machines, install and start using them, you notice some strange notes,stuck to their back panels. They read like this: 'If you charge a fee for any bearing or other work you generate using this machine (a “Work”), you may only sell or distribute such Work through Mr Gregory Bapple (e.g., through the his bearing store) and such distribution will be subject to a separate agreement with Mr Gregory Bapple.'
I think there'd be liters of spittle, spit while arguing about the presence of any common sense in that 'back panel agreement' you haven't signed when buying the machines. Mr Bapple's point would be that 'You have agreed to the conditions, layed out in this document, by the very fact of using our machines.'
Nonsense? Yes. But that's exactly what Apple wants us to believe when we start using their newly released iBooks Author.