AABrowse is a server browser for America's Army written in QT. It supports both Gamespy and Andromeda master servers, buddy lists, favourites, and player search.
Big Brother Bot
BigBrotherBot (B3) is a cross-platform, cross-game game administration bot. Features in-game administration of game servers, multiple user access levels, and database storage. Currently include parsers for Call of Duty (CoD) and Call of Duty 2 (CoD2)
ClanMod is a Metamod plugin designed to offer extended features to Half-Life server admins by providing an in-game menu system, scheduled tasks, custom command and task declarations, specialized configs and addons to ease the admin's task of administration.
Echelon is a Gnome panel applet which monitors a user supplied list of game servers. The primary purpose is to watch the servers for the presence of specified player names. Echelon is written in Python and uses GTK and thereby requires a recent version of gnome-python-extras.
gLuV - gLu's Voyeur - A web based server monitor for multiplayer games. PHP based, so gLuV does not need a browser plugin to view.
A console game server browser which is able to retrieve the online servers by contacting the master server, master.gamespy.com. It supports over 700 games and has many options and features, including the sending of heartbeats, the filtering of the servers list (for country, name, port, players, and more), the launching of a specific application for each server found, the querying of a server, an update option for the latest supported games, an output selector (for possible GUIs), and more.
GtKali is a free Kali client for Linux using the Gtk+ toolkit. It's designed to provide an X interface for the kalinix library provided by Jay Cotton.
GUTS is a single program which provides the following GUI tools for Unreal Tournament 2004 in Linux: a cache manager, a umod unpacker, a uz2 compressor/decompressor, and a dedicated server launcher.
HLMaster is a fully automatic master server for Half-Life based gameservers. Features include: Automatic addition/removal of gameservers, Ability to load your own list of gameservers, Loadable IP-Filters, to keep unwanted gameservers out of the list, and a custom gameserver limit.
KRconLinux is a KDE tool for querying, managing and browsing game servers like Half-Life mods (Counter Strike, Dod, etc.), Quake series, and more. It features a console to send rcon commands, a server log receiver, an (incomplete) IRC bot to monitor the games, and a chat console to interact with the players inside the game. It is capable of listing the available server maps and changing them, establishing server settings via configuration files, changing the current server password, updating and modifying the server ban list, kicking and banning players, and changing server variables.
Multistat is designed to be a flexible log file parser for multiple game servers. It is designed with an extensible plugin interface, thus allowing for any combination of input or output (i.e. Quake 3 input with HTML output or Halflife with HTML output).
OpenSimulator is a multi-platform, multi-user 3D application server platform. Out of the box, it can be used to simulate virtual environments and worlds similar to Second Life.
PvPGN (Player vs Player Gaming Network) is a bnetd based gaming network server emulation project. It currently supports all Battle.net games (such as StarCraft, Diablo II, and Warcraft III), and most Westwood Online clients (Tiberian Sun, Red Alert 2, Yuri's Revenge). It gives you the power to run your own server, manage your own users, run your own tournaments, etc.
QStat is a command-line program that gathers real-time statistics from Internet game servers. Most supported games are of the first person shooter variety (Quake, Half-Life, etc).
quaqut is a multiplatform program, written in C, that queries Unreal Tournament 2004 (?) game servers and retrieves information such as server name, game type, current map, names and scores of the players, etc.
SunUO is a free Ultima Online server for Linux/Mono and Windows.NET, based on RunUO. Ultima Online is a commercial MMORPG by Origin / Electronic Arts.
Ultima Offline Experiment
Ultima Offline Experiment is an Ultima Online Server emulator.
uoamhub is a dedicated server for UOAutoMap.
UT2003area is a set of tools for querying Unreal Tournament 2003 servers and extracting information such as the server configuration and the list of players.
wmQStat is a dockable front-end to qstat by Steve Jankowski, a popular command-line monitor of lots of Internet game servers, i.e. Quake/W/2/3, Hexen2/W, HL/CS/HL2, Tribes/2, RtCW, UT200x, DooM 3, FarCry, to name a few.
XBashServ is a program written in Tcl to help set up and run game server programs and some other general network server programs on UNIX systems.
Quake/QuakeWorld/Quake2 server browser and launcher for Linux/X11