I think I found the error.
Try to use an armature modifier instead of a constraint.
For testing I suggest pview:
pview -lc door.egg -a door_open.egg
The -l makes pview pop up immadiately and load your model afterwards. -c is same as pressing c in pview - it puts your model in the center of view. The -a flag allows you to specify an animation file.
To actually see it shaded, press “l” (small L) in pview.