From his e-mail:
We just have finished the translation of a new YafRay document into English. The original is based on a lecture that Alejandro Conty gave last June.Â That lecture was also based on this YafRay paper, although in this [new]document everything is much better explained and there are also some extra tips.Â The document is not just about Yafray, it explains general concepts about raytracing and Global Illumination that are applicable to other similar render engines. Luis, Claws, and I have collaborated in this translation.
Yafray is certainly alive with documentation, and this lighting discussion is certainly a great addition to understanding YafRay and lighting.