[ItsABytecode]

So no 3rd party client software unless the company running the service gives explicit permission?

No 3rd party batteries in devices or 3rd party ink cartridges either

[zamadatix]

It generally doesn't cost e.g. the printer manufacturer anything when you use a 3rd party cartidge. This is separate from the value/loss described above. I still think once you reach a certain size there need to be some interop requirements though but I can also see why many would say these points are unrelated to iMessage.

[sbuk]

> So no 3rd party client software unless the company running the service gives explicit permission?

That's about the strength of it. Unless the protocol is open, paid or otherwise. iMessage is closed and undocumented.