You can kill the program camera-ui, but then you'll need to launch the the camera application manually when you do want to use it. The command to kill the program is:
You can also chnage the name of the signal generated by cover opening, thus preventing camera-ui from jumping to front when the door is open. Discussion of how to do this is here:

http://talk.maemo.org/showthread.php...516#post495516

But you need platform_cam_shutter instead of platform_cam_launch.