[font=courier new]YafarayRenderer.h[/font], [font=courier new]YafarayRenderer.cpp[/font] and any source files like Java ones are not necessary for a plug-in to work. I just took the habit to include source code in the plug-in to avoid developers to download it from another place (these files are generally not very large).
SunFlow and YafaRay renderers are completely independent from each other, so you can organize the packages where you use them like you want.
The only thing to take care of, is too update in the YafaRay program according to where the DLLs it requires are stored, so the plug-in can find these DLLs to extract and load them.