FYI, I've just put UberPOV back on the tracks.
The current development version includes all the latest and greatest
from the POV-Ray 3.7.1 "master" branch, plus the advanced diffuse models
(Oren-Nayar and Lommel-Seeliger), and can be found here:
https://github.com/UberPOV/UberPOV/releases/tag/v1.37.1.1-alpha.8756754
