What are the requirements for use in a mobile application, or any application for that matter. there was no mention of that in the short PDF, Mobile apps often follow the web specifics but not always?
A simple rule of thumb that works in most cases is "If the image is the product then you can't use it. If the image is part of a project then it is most likely fine."
I can't think of any mobile app situations where it should be a problem unless you are offering the image as a download.