With Firmware version 3.3 the udev rule is not needed anymore. My Linux system (Mate 1.8.2 on Ubuntu 14.04) was able to access the files without the rule.
The Parrot Bebop drone can be connected via USB to a PC and acts as MTP device.
Unfortunately, Ubuntu 14.04 did not automatically detect it. I had to create a custom udev rule to make it work:
ATTR{idVendor}=="19cf", ATTR{idProduct}=="5038", SYMLINK+="libmtp-%k", ENV{ID_MTP_DEVICE}="1", ENV{ID_MEDIA_PLAYER}="1"
Put this into /etc/udev/rules.d/69-libmtp-parrot-bebop.rules, restart udev via $ service udev restart and re-plug the drone to your PC.
I've also opened a bug for libmtp so that the drone will be detected automatically in the future.