The "same source" notation is really not a good one. A better way to think of it is this: every time there's an unnamed bonus, it's actually an "X" bonus, where X is the name of the effect. So if you have two orange prism ioun stones, they're both giving you an "ioun stone bonus", and won't stack. In this case, it's a "draconic aura bonus".
(Note: this is not official terminology in any way. But it makes more sense than their language.)