At the time, everyone pretty much assumed that the ebooks would be free with an Amazon Prime membership. It would work similar to the free streaming video that Amazon offer now. As you can see from the code above, Amazon are clearly planning ahead.
There's also code later in the page that (should Amazon ever offer this service) will be part of a menu. There are 2 menu options named, and they mention returning and deleting these ebooks. They would work much the same as the library ebook options work right now and in fact they say exactly the same thing.
All in all, this is an interesting confirmation of that older story but it's not actually new.