These Beeper folk sound a bit entitled. As was repeatedly mentioned in the other thread [1], building production applications on top of an undocumented and unsupported (in terms of backwards compatability, etc) API is a nightmare that should be avoided. Apple has every right to change their API, if they do Beeper will go down, and Beeper will blame Apple. I understand Apple's incentives to not want to be in this situ…
Then don't use Beeper.
> I trust an established, trillion dollar company far more with that sensitive info than I do a fast-moving, eager-to-break-things startup. And the list goes on.
Thankfully, you don't necessarily have to trust them since the entire process runs on your device.
> I really don't believe they're entitled to parasite off the undocumented iMessage API.
Do you also believe it's "parasitism" for a tool manufacturer to create a screwdriver that fits another manufacturer's screw shapes? That's more or less exactly what's happening here - they made a tool that fits the existing proprietary API and interacts with it.