In all sincerity, how useful is an open source iOS app? Don't you still need to pay their $100/year fee to distribute it? Wouldn't you have to jailbreak your phone just to install this yourself?
I recently took a course in college for iOS development, and because of open-source code I was able to ace the class and get picked-up for potential funding on the class project.
Yes you need to pay Apple the $99 to get it on your own device, and no you don't need to jailbreak (unless you want to circumvent the $99). Plus there are other ways to get the app on your device without paying or jailbreaking (creating your certificates, etc).