Dude - let me make this super simple. These rendering pipelines import the SDKs and APIs they connect with. The pipelines have tons have high value custom code. Under the GPL, they have to be open sourced if they use blender - this is 101 stuff. And under GPL it is viral, if stage 1 is now forced open, the next big set of stuff that integrates with stage 1 is also forced open and so on.

Pixar is not open sourcing their pipeline - period. Do you not understand that these companies build giant and high value software around the various engines?

Listen - I didn't realize how little you understood. This is actually covered in the Blender FAQ's because it can really bite you (even if a small player) if you build an add-on to blender.

"Blender’s Python API is an integral part of the software, used to define the user interface or develop tools for example. The GNU GPL license therefore requires that such scripts (if published) are being shared under a GPL compatible license."

This is cool if you want to use stuff - they make that clear too. "Sharing Blender or Blender add-ons or scripts is always OK and not considered piracy." But for commercial players this is an absolute no go.

This is not FUD, this is hard reality, and no commercial player is going to tie into something like this.