I don't understand how it works from that website. Maybe it's evident to Kindle owners, but from the outside it makes little sense. E.g. the "(absolutely risk free)" in the "Lend a book" button as opposed to "(always free of charge)" in the "Borrow a book" button makes me think there are hidden charges or something shady going on. Or maybe it's all free, or these charges are just evident? I don't know.