Not only did they theoretically forbid it, they actually took something very close to this out of the app store: this app maker is based on Scratch and there us

Not only did they theoretically forbid it, they actually took something very close to this out of the app store: this app maker is based on Scratch and there used to be a Scratch player for the iPhone (it wouldn't let you create Scratch programs on the iPhone, but it would let you run ones you had made on your computer) and Apple removed it from the App Store.