Are there converters to Use Blender Files / Animations with other (free) Renderers (POVRay, BMRT for example)?
Yes, with all of them:
Have a search on this forum… you’ll find the answers, and on Python forum too.
I use LightFlow, and I’m pretty happy with it.
Stefano
I’m curious what the added benefit is of rendering in another application. Specifically, what gain you would get vs. the pains of doing so.
Atomike
Blender is a scan line renderer, this makes it fast, but does not allow for considering true physics of light.
You don’t have refractions and reflections (You can fake them, but only reflections from planes and sphere are acceptable)
An external renderer capable of ray-tracing can handle that.
Look at my site (link herebelow) there are pure Blender and Blender+LightFlow images…
Stefano
Hehe, I see no link. 
Imp
DoubleHehehe that small house at the bottom of any post of mine 
Stefano
too bad most of these non-gui script is mostly for those
who can coding…I am not an coder and I hate all those
f****n code scripts…it never works !! or it will never be any good :x
Doh, lol
Good stuff… real good stuff.
Imp
i use virtualight, also very happy with it
for results check my site
for more info about virtualight check http://www.3dvirtualight.com
have phun!