And I know that ultimatums have been issued by the DAZ PtB's constantly over the last few years.

This is rubbish there have been no Ultimatums issued by Daz 3D to anyone. Even if that was so, why would it effect what vendors create on this site? The truth that you clearly don't want to face is that many vendors PA's are moving on to the greener grass. I think you are misunderstanding how the interaction works between the parties. If Daz 3D was involved in the practices you are suggesting why would they not just insist that all of their PA's become exclusive to Daz 3D? Why? Because their PA's have the freedom to create whatever they choose, supporting whichever platform they choose and are free to be involved with any market they choose, even multiple ones. Sounds like freedom to me.

Enough so it is clear the DAZ site is NOT a "free and open" environment in any area.

What are you talking about, the only place that is entirely "free and open" is inside your own mind. Everywhere in a modern society is governed by rules of some kind. Having rules in place to maintain order, isn't a state of denied freedom. Maybe I should ask what it is you feel you are not "free" or "open" to do on the Daz 3D website? Judging by the way you are trying to paint Daz 3D as some kind of evil overlord cracking the whip over sweating, starving content creators. I can see how you would quickly run afoul of the mods & TOS there...

Honestly, most of what your saying is unsubstantiated speculation, and somewhat biased to suit a particular version of reality(fantasy). The reason many vendors have been switching to DS, as has been stated by the very same vendors numerous times, financial. If the market for Poser products was still purchasing with strength, its market base would be hard to ignore for vendors or PA's and there would be no reason to "switch to DS". On the other hand to continue producing product for a market where returns don't meet the work involved or returns are higher elsewhere, is the niche of hobbyist and enthusiasts to pursue. It doesn't require "coercion" nor "ultimatums" for most people to realise when they need to change or be left behind, especially if their livelihood depends on it. And despite what you say Daz 3D are currently upping support for Poser products and it will ultimately be up to the Poser market whether this push succeeds or fails and if it will continue into the future. As it is here and in most markets.