I don't see how MobileReference could have permission from the copyright holders to publish Animal Farm, particularly since they were selling this for $0.99. See
You really DON’T own your Amazon ebooks.
I have ebooks that I bought in the Kindle Store but are no longer available for sale on my Kindle, and Amazon has not removed them. It is a bit different when the ebooks are bootlegged though, Amazon probably wants to be squeaky clean on copyrights.