This is exactly why I think the quote "I'd Rather Beg Forgiveness Than Ask Permission" should be carefully avoided when you depend on 3d parties, API, etc.<p>I always explicitely ask API/sites (Amazon included) owners whenever I have a doubt.<p>What do we have here - Amazon terms:<p>"The use of a mobile application
in conjunction with the Product Advertising API or the Associates Program without our express prior written approval is not permitted."<p>Which leads to this interpretation:<p>"Here's my understanding of the situation:
- Amazon does not seem to allow the usage of any Amazon data in mobile
 applications, any data that was once downloaded from Amazon."<p>My interpretation is different: Amazon does not allow the usage of mobile xxx, <i>unless express prior written approval</i>.<p>So I really think this story tells us something: if you work with someone, get in touch, ensure the situation is clear, then go on with your project.