bnetd is a software package that was reverse engineered from Blizzard Entertainment's Battle.net online multiplayer gaming service, providing near-complete emulation. The software allows users to create and play games on their own servers, instead of Battle.net servers. Released under the terms of the GNU General Public License, bnetd is free software.
Due to a United States lawsuit won by Blizzard against bnetd's original developers, they no longer maintain or host bnetd.
Read more about Bnetd: CD Key Non-interoperability, Blizzard Takedown Demand and Lawsuit