http://www.coala.uniovi.es/~jandro/noname/
Yafray
http://heroinewarrior.com/cinelerra.php3
Cinelerra
Buy the full 3ds max edu. if you must use it.
Also check out full older versions of 3d programs included w/ magazines.
3DWorld inc/ Cinema 4d CE in issue 43 (it can export to 3ds)
The only restriction is the render output size of the images to be just below the PAL (standard : 720x576) and NTSC (standard : 720x486) formats.
So no hi-res

Houdini Apprentice has a VERY small watermark that you can just crop out when you are done...
Out of all of those i would pick the houdini apprentice-
http://www.sidefx.com/products/apprentice/index.html
Of course if you do plan on buying houdini master it will cost 17,000
Houdini Select is only 1,299