oooh! Tough call.
California is a right to work state.
If his contract is like the contract I had to sign, then there's usually two sections regarding a non-compete clause.
One is overly broad and not worth the paper its printed on. (It usually restricts an employee from joining a customer of IBM or a company that has an existing relationship with IBM.)
The second is used to specifically identify a competitor. Like Oracle or Microsoft. This clause is a bit more enforceable, at least in most parts of the US.
From memory, in California, if the person works for a competitor but isn't working in the same area or on the same technology, they should be ok. At least that's how it worked out for some guys who worked for a couple of hard disk manufacturers ...
As to poaching a PowerPC guy... If I were Apple, I'd look more at the Cell chips and technology than PowerPC. ;-)