To each their own but it is kind of dangerous to download the iOS app from anywhere except from DJI. Since the app is adhoc still, anyone can throw together an app, call it the pilot app, and since you will install it agreeing it is from an untrusted developer, it can do all kinds of stuff to your iOS device.
IMHO, either wait for the Apple App store release or get direct from DJI sight. If your serial does not work, contact support instead of clicking links to some website other than DJI.
My .02.