A recent story on Daily Radar quoted an unnamed source at Sega who when asked if the Dreamcast port of Half-Life would include multiplayer said, "I believe it won't." After reading this, we got in touch with Gearbox Software's Randy Pitchford, who made the following statement, which says that they intend to attempt to include a multiplayer mode:

Our goal is to take advantage of every unique Dreamcast feature - from the advanced graphics capabilities to the on-board modem - in an effort to make this title amazing. As far as I know, a first person shooter has never had a robust online multiplayer component on a console, and we'd obviously like to be the first to pull that off.