A login is required but the source is available
https://devzone.parrot.com/repositories/entry/oss-ardrone2/trunk/linux.tar.gz?format=raw
Configuring the environment for a build is here http://tjworld.net/wiki/Linux/Kernel/ARMCrossCompileOnIntel
make -j2 O=../builds/ardrone CROSS_COMPILE=arm-none-linux-gnueabi- ARCH=arm EXTRA_AFLAGS=-mfpu=neon menuconfig
Some build issues I hit are covered here http://www.idroidproject.org/wiki/Compiling_a_Kernel