I'm just following http://www.jamesmolloy.co.uk/tutorial_html/.
The code should run fine under Ubuntu 13.04 though, I've had to hack a bit the tutorial (mainly the bochs config).
The linux-0.01/ directory has been downloaded at https://www.kernel.org/pub/linux/kernel/Historic/linux-0.01.tar.gz and is probably under GPLv2.
Files in the src/ directory comes mostly from the tutorial (for each exception the license header have been retained in the concerned files) so consider it under CC0 (see https://creativecommons.org/publicdomain/zero/1.0/).