Why do I need an iOS certificate just to publish a Flash file for AIR for iOS?

I was completing a gotoandlearn tutorial called Tablet Swipe Gestures - Learn how to respond to swipe gestures by building a nice photo gallery for the iPad


I get all the way to the end, and find I can not publish my file because I do not have an iOS certificate. I am just learning at this point, do I actually have to pay to get a certificate?