It is an additional tool for the Local Adjustments module,
It’s called Color appearance,
It has 2 parts: Cam 16 and JzCzHz (which can be combined or used individually),
It can be integrated into some of the other LA tools instead of using it on its own,
JzCzHz (JzAzBz) is a replacement for Lab (sort of). It is better suited to handle higher dynamic range images and wide gamut,
It uses Ciecam 16 (No ciecam2) and is put later in the pipeline, which should make it less artefact prone then the current Ciecam 2002 module.
There’s already some documentation with more technical details. In French only atm, Wayne is working on an English translation: RawPedia - Color Appearance [fr]
Just to reiterate: All this is still experimental/in development and not integrated into the development branch. I’ve been doing some testing and bug-hunting for Jacques and issues do show up and parts are still being changed/tuned at the moment. So, do not integrate this as of yet for serious editing.