Two weeks ago, NetBSD 5.0 was released. The Dreamcast port was updated by Marcus Comstedt (as far as I know).
The list of changes between the 4.x and the 5.0 release is too long to post it here, you can find the full changelog here.
NetBSD 5.0 for Dreamcast can be downloaded here (.iso file) or here (.torrent).
The official website is here: http://www.netbsd.org/ports/dreamcast/