hum, unless there exist some way that can be done using only external code, without hacking Blender sourcecode, for instance by some render/Blender UI API, an integration like YafRay 009 is not possible and it does not make sense anymore.
Besides the guys running the YafRay project now (me included) think than in the long term the less we depend on Blender politics and decisions the better, though maintaining a good relatioship with everybody. We want to run YafRay like a truly independent project but intended for the Blender comunity and for other open source modellers like Wings3D (I hope).
Since there seems to be no resources enough to finish the render API for Blender, then the most logic workaround is using Python to get scene data and to collect enough information (through a python coded API) for yaf(a)ray to render.
We want to ditch the Blender special compilations way because there are constant changes in the Blender code (thus we depend on Blender guys decisions) and because special compilation scare away users.