Serious question: could they be sued by Hemingway's family for using his name on their product? I mean, if I made an app called "Tolkien" I might realistically run into trouble with his estate.
Looks like they acquired proper licensing. The footer of the webpage states: "Hemingway™ is a trademark of Hemingway Ltd., used under exclusive license through Fashion Licensing of America, Inc., New York, NY 10001"
Fashion Licensing of America's site states that the company is the exclusive licensing agent for Ernest Hemingway and F. Scott Fitzgerald.