That's a kind of odd use of “non-partisan”—both (a) and (b), actually, since (a) would allow a commission entirely of political appointees of the sitting governor, without in-law specification of partisan makeup, to be a “nonpartisan” commission, and (b) allows a commission where appointment is specifically slots by party and most seats assigned to the two major parties to be non-partisan.

But, yes, by that odd definition, the California system is non-partisan under (b).