Due to some discussion in which I inadvertently landed with James Jacobs (of Paizo) I suggested that I believed that Paizo's use of Tiamat (as well as Orcus and Demogorgon) was based on IP issues. That is, although all three names are public domain mythological figures, the specific interpretation of them through D&D is not, and Paizo probably wanted to leave open the possibility of gamers using the D&D versions in their personal games without coming up with unique interpretations of the name for Pathfinder that contradicted the D&D ones.
Jacobs essentially said that this was 100% correct, although they did use some other names to get a lot of the same concepts/aspects in print. For example, the Paizo Demon Lord and goddess Lamashtu is meant to specifically invoke several of the concepts of Demogorgon, without necessarily stepping on Demogorgon's toes so much that you couldn't also have Demogorgon in your game if you wanted to. I told him that I had thought Angazhan looked more like a Demogorgon analog to me, and he admitted that it had evolved somewhat coincidentally into those similarities; Angazhan was originally conceived as a more fantastical, demonic version of King Kong. Because there is no Demogorgon, Angazhan ended up taking on some of Demogorgon's vibe in that regard (as well as that of another D&D demon lord Ilsidahur.
See posts #6 and #9 in this thread for the full details. In #9, Jacobs referenced the Paizo reinterpretation of the Isle of Dread--I actually own two copies of that particular issue (for some reason--although I'm not sure where the poster map might have gotten two in the meantime) so I pulled it down last night after that brief online discussion and flipped through the small article on the island (I didn't read the actual adventure again--at least not yet.) Frankly, I'm kind of excited about the possibility of the Isle of Dread. It's very obviously D&D's homage to King Kong's Skull Island--not that there's anything at all wrong with that. Add in some demons to make things even more interesting, and off you go.
As a gaming concept, this sounds at least as interesting to me as the SOLNOR concept I just proposed. Which is exactly how I never finish anything up by being distracted by new ideas. Dang. I thought of mixing it freely with Freeport, the pirate setting of Green Ronin. Freeport being near to--but separated by consistently and maybe even supernaturally difficult seas--the Isle of Dread and serving as a potential base from which to launch exploration of the isle, is a great idea to me.
Of course, I don't really need to specifically develop this idea. I've already got Porto Liure, which started off as pretty much the same concept as Freeport, but which matured and evolved--much as Demogorgon matured and evolved into Lamashtu in Paizo's setting--into something unique. And I've got the Demon Isle--:L'Isula Dzovençan--which would come across as a kind of hybrid of Iron Kingdon's Cryx, the Isle of Dread, and Paizo's The Worldwound all wound up into one petite, compact package.
While I've got two campaign ideas kind of going off on each other simultaneously, one is really an all new setting noodling project, while the other is turning an existing setting into a playable campaign with slightly different themes. I think there's room for both, right