I know nothing about this application, but I've bolded what is likely the answer. I imagine the terms of use will spell this out in vague and convoluted language somewhere aroudnd 2/3's of the way through the 400 page document. Nothing is free, and they have to monetize the platform in some way.
Apparently though, there have been a lot of copyright issues with this platform, and some content developers are getting screwed:
http://www.theverge.com/2012/3/30/29...sharing-change
http://brooksreview.net/2012/03/explanations/
Instapaper might be a good alternative for you.