> Suppose that a developer discovers a bug in the Apple Music API that allows songs to be played without paying for the Apple Music subscription. Are you claiming that if a developer writes an app to exploit this bug, they're not doing anything illegal? It's ok to get Apple Music without paying, as long as you're just "calling an API"?

That would be illegal, yes, but for an entirely different reason (DRM bypass to get copyrighted material), not because it's calling an existing API. It's not the case for 99% of apps.

> In any case, you're still ignoring distribution. You start with the assumption that a binary is already on the iPhone. The technology is already inside the iPhone, but the third-party app is not. Distribution is an entirely different legal matter than personal use.

The third-party app does not contain any Apple-owned or licensed technology just because it's programmed to make use of it once inside a phone, and there's no IP right to control distribution of material that uses proprietary technology if that technology is not actually in the distributed material. The only barrier is Apple's own actions in how they programmed iOS to reject unsigned code and their developer program, not a legal one based on IP.