3.2.1 — Acceptable business models

This is the "allow list" side of Apple's business model rules — standard approaches like paid apps, in-app purchases, subscriptions, ad-supported free apps, and enterprise or B2B distribution are all explicitly fine as long as they follow their own specific rules elsewhere in the guidelines.

Rarely cited on its own — usually referenced alongside a more specific rejection, like 3.1.1, to point developers toward the approach that would actually be acceptable.