Yabause is a Sega Saturn emulator under GNU GPL. It currently runs on FreeBSD, GNU/Linux, Mac OS X, Windows, Dreamcast, and Wii.

Release notes:

Controls code has been rewrote to enable emulation of the two peripheral ports of the Saturn. Software renderer also got a major update with window, line scroll and mosaic now emulated. Preliminary support for translations has been added too.

Thanks to http://www.dreamcast-germany.de/ for the news.