If it's brown, it's probably not going to change color again. It's ripe. You can save the seeds and eat it.
Many hot peppers, though not ripe when green, are still usable for culinary purposes when green (some may taste better green, or some color that isn't their final color)—but you'll want to wait until they change their final color (or at least start to do so) before you save any seeds.
I've never heard of a pepper with chocolate brown as something other than the final color it ripens. (Although brown-ripening peppers can ripen red or reddish brown sometimes, and not to full-brown at all; whether they're red or brown, they're still fully ripe.) If you leave the peppers on longer, the ripening process may continue and possibly lose or gain flavor (but the color should stay pretty much the same, and it's still ripe when it first changes the final color). If you leave it on too long, some of the seeds may rot.
Plus, the link you provided at Cayenne Diane's does mention that the fruit turns brown when it's ripe: "Ripe pods are brown in color, with the white internal membrane covering much of the inside of the pepper."
Most sellers of peppers that go through multiple color phases seem to me that they advertise the fact, since it can be a selling point (although maybe not all of them).
Although there probably are several, I haven't heard of many Capsicum chinense peppers (especially among the super hots) that have more than a 2-color ripening cycle. Usually those seem to be other species.
So, in summary, I suppose it's possible it might change other colors and that it's not ripe (I don't know all things, after all)—but, from my observations and experience, it seems very unlikely. It would have to turn brown again after it changed another color for that to be true (since the description says it's ripe when it's brown).
Now, if it's merely a tan-brown rather than a chocolate brown, then I'd wait, if you want to save seeds.