Rui Paulo built a NetBSD/dreamcast LiveCD without X11 (the *nix GUI). It has only the base system without any packages.
Wouter Schoot, Jo?o Santos and Jo?o Pinheiro have provided mirrors for the 50MB download as follows:
http://netbsd.student.utwente.nl/rpaulo/
http://fnop.net/dreamcast/
http://phlox.ptblog.com/