I already gave you my answer some time ago:

sorry I became a fan of sunflow when I see the gallery (previous link 4) and User manual (Previous Link1). For a quick user like me, it is fast, simple, editable and indirect support with OBJ when compared to other render engine like python. Especially its ambient-occlusion pass is superb, may be more than v-ray.(I would like to say Thank you to SweetHome3D for introducing this render engine to me.)
I think you are just skiping its some other features like preset primitives(sphere, cylinder, hair, particles), directionalspotlight, spherelight, trianglemeshlight, IrradianceCache GIEngine,multipassRendering, HDR and tga image formats.... Sunflow requires just apply its values as it need.(that I wish).

SunFlow is not maintained by its main developer anymore.

I think sunflow engine utilized Java3D at its peak point with the current version or a bad luck with the developer.
[may I know which program that will make it as a new render engine for future in your mind.? [<):)] ]

I just can't imagine how long it would take for a real Sweet Home 3D scene!!!

I said if the scene using a sphere as alight source then sunflow counting its vertex points and started emitting light from each it. According to smoothness of the sphere number of vertex may vary. It is an example of light source as sphere(760 vertex) that take 1Hr20Min. Instead of sphere we can use triangle(3 vertex points)mesh or rectangle(4 vertex)mesh can use as a light source which takes almost 20-30 sec. I have a surprise for you.
I found a logical error/bug that does not rendering glow(/fake light).
here is the proof:

There is a one more OBJ material parameter called "Ke". [*-:)]
If Ke(emission) is derived then "illum" value become ignored and object consider as glowing.
Ke is expressed in RGB form and its value normally lies '1' and '0'(no glow).Also you can go beyond '1'.It express like
Ke 0.0 1000.0 0.0 //emit green glow and will appear in wider area.
If Ke is not set then glow is indicated by setting illum value as zero and Kd
illum 0
Kd 0.0 1000.0 0.0
I think the OBJLoader.java failed in this step , It ignores illumination value when it is zero, also does not handle a parameter 'Ke' is active.
So the program always bypass these steps(condition 1 , condition 2 ) in photorenderer.java