Unfortunatelly, as you mentioned, Asctec eliminated all the manuals and software from their webside. However, there is a github repository that permits to control de Asctec Firefly UAV in ROS (the Asctec Hummingbird as well).

Here is the repository:

https://github.com/ethz-asl/asctec_mav_framework

And here you have the wiki that explains how to install it and how to use it:

http://wiki.ros.org/asctec_mav_framework

In my opinion it is better to control the vehicle with ROS rather than with the Asctec SDK.

Also, I recommend you the RotorS simulator in ROS/gazebo, which has a model of the Asctec Firefly. I think it is nice to test the algorithms here before implementing them in the real platform:

https://github.com/ethz-asl/rotors_simulator

http://wiki.ros.org/rotors_simulator

Hope it helps you,

Bartomeu

Thank you Bartolomeu, I was a bit skeptic about ROS package because it seems to be unmaintained, but surely you're right: it's the best available options. Do you know whether firmware updates are needed?