Under Linux, one needs gphoto2 in order to download photos from the camera on USB. And one also needs usbfs mounted to /proc/bus/usb and of course one needs proper permissions. For example on current Debian unstable I had to add this line to /etc/fstab:
none /proc/bus/usb usbfs defaults 0 0And one also needs a user accessing the camera to be in group plugdev. Permissions on devices in /proc/bus/usb/... are set by some of beasts like udev/hal/wtf. No matter, plugdev did the trick for me.