Just gonna weigh in and clarify a few things.
by way of introduction, I'm one of the greybeards of the DS community, and a founding staffer of athas.org ...
First point: Monsters. There's a very simple reason that Dungeon didn't look at or consider our published monsters: They weren't published when the article was written. This is a magazine folks; they have to do a lot more layout than we do. The article deadline was probably at least two months before the print run began, and there were probably a couple of rounds of editing that went in before that.
While portions of Terrors of Athas have been available for a long time, they were never really published ... preview versions, and some individual monsters, yes, but not exactly easily available. The full version wasn't posted until a month ago. There's no way it could have been used, or referenced by, Dungeon.
Second: I spoke to the Editor in Chief at Pazio several months ago. He informed me that Dave Noonan has made it a point not to read or consult any of the athas.org material. This is likely from a CYA perspective, in the case that we might decide to flip out an accuse him of stealing our work ... or to avoid doing so subconciously.
Because of Dragon/Dungeon's publishing policy, they couldn't take the approach of just talking to us first. Essentially, they can't/won't publish anything that has been published elsewhere (even on the Internet) ... some kind of Copyright issue; I think they claim ownership of all submissions.
Third: The terms of our original agreement with Wizards state that all of the Dead-Worlds sites were the custodians of their particular world, and were authorized to produce official material. There are certain limitations on this:
We can't make money off the setting. If we charge anything for products, it's materials only. Our primary method of distribution is on-line. We can't kill off or otherwise majorly affect any iconic characters. We have to use D&D. We can't run our own services (bbs, web-based chat, etc), we're to direct fans to the WotC provided boards.
Not everything published on the site is official: only our PDFs are actually considered to be official products (not a WotC policy there, it's one of ours).
I'm not demanding that Pazio should have used our material. I understand the reasons and the rationale. I would have liked it if we were invited to help contribute.