So Sketchup or FreeCAd can make the conversion DXF OBJ ;) (in free)

http://www.freecadweb.org/
http://www.sketchup.com ... + http://rhin.crai.archi.fr/rld/plugin_details.php?id=790 (obj exporter plugin)

http://www.brothersoft.com/downloads/sketchup.html?fromsearch maybe only old free version import DXF so take the V6 ;)