While I'm sympathetic to wanting to discuss legal issues here, as legal problems are a large facet of being an independent developer, in general questions that are not about licensing (and generally, that means FOSS licenses like the GPL) are off-topic here for two reasons:
Our expertise is not in IP law, contract law, or any other type of law. We would be giving legal advice as laypeople, which is an opportunity for a bag of hurt.
Even putting aside the expertise, questions do not provide enough detail about their specific situations to be able to provide accurate legal advice. The ones that do are so specific to the asker's situation, they're too localized.
That is, given the diagram:
They're hitting the center, "Just You" part, not the blue, "All Programmers" part. There are very few legal questions that are generally applicable to programmers at large: well-known licenses like FOSS licenses are probably the best example of what would be.
But to speak to this specific question, there is exactly one entity that knows what will be accepted, and that's Apple. From the App Store Review Guidelines:
- We will reject Apps for any content or behavior that we believe is over the line. What line, you ask? Well, as a Supreme Court Justice once said, "I'll know it when I see it". And we think that you will also know it when you cross it.
- This is a living document, and new apps presenting new questions may result in new rules at any time. Perhaps your app will trigger this.
We're not going to even begin to provide a definitive answer about this: Apple decides for themselves what's going to work. If there's a concern about what they will and won't allow, they need to be asked: not random strangers on the internet who are not in the know.
I know there's a cost associated with joining the iOS Developer Program: I get it. But just like we're not a substitute for a lawyer when someone can't or won't pay for one, we're not a substitute for Apple when someone can't or won't pay the iOS Developer Program fee.