So for all the comments saying they need to update, don't worry, they will. The lineup, stages, and times just got released online on their website. They are very particular to hold off until about a month before to make sure everything is in place for the artists before signing times. That way they don't have to change it everytime there's a cancelation, etc.
I've gone to jazz fest for the past 5 years, and every year it gets better! The app is essential if you want to preplan where and when you want to see specific artists. If you just want to sit at one of the big stages all day, to save a seat for the big acts of the evening, you don't need this app. But if you want to experience local musicians, Indians, food presentation, etc, the app is essential.