The NetBSD Project is an international collaborative effort of a large group of people, to produce a freely available and redistributable UNIX-like operating system, NetBSD.
NetBSD/dreamcast is the port of NetBSD for the Japanese game console SEGA Dreamcast.
The changelog is very massive and can be found here: http://www.netbsd.org/releases/formal-5/NetBSD-5.0.html
Thanks to http://www.dcemulation.org for the news.