[KuraFire]

…that the article and board members in question are willing to reveal.

It's still entirely possible (and more likely if you ask me) that the Prop 8 angle and subsequent objections raised by many Mozillans and Firefox developers have changed their minds about this, but these are big-time board member CEOs we're taking so of course they're not going to say the political position on Prop 8 of the newly appointed CEO is what's making them resign. That's still a bad career move in today's world, but saying "we wanted someone from outside the organization with experience in XYZ" is not.