Didn't most people assume that Apple is looking for someone to work on a new Apple device to run a modified iPhone OS, like a new Apple TV?
It seems to me that Apple is going the other way than opening up availability of the iPhone OS. I think PA Semi's job is to design and build custom, optimized chipsets out of available components (ARM, PowerVR, et al.) with built in anti-hacking measures. Apple is going to avoid getting into the problem they had with the Motorola PPC CPU, by relying on the market to provide components instead of relying on one company's CPU design, which can't compete against the market as a whole. ARM and Intel are basically going all out for this market space; ARM is being very aggressive in promoting its components(as the Open Pandora itself shows), and Apple got a lot of performance out of the ARM-architecture CPU.
And, Apple can avoid another confrontation like the one they had with Psystar by making the iPhone OS incapable of running on anything except Apple hardware. Their goal is to make a family friendly, semi-closed environment for personal electronics, entertainment, and digital content -- like Disney and Nintendo, but working with what they have already built up. Apple can probably do this because it has so much IP in multitouch technology and a huge design advantage, as well as a huge amount of money and a large user population who can run apps on any one of three devices so far: the iPhone, the Touch, and the iPad (when it's released).
Anyway, that's my current Apple conspiracy theory.