Cardpics is a set of free cards sets for use in programming card games.
ClanRPG will be a tool for easily creating Role Playing Games released under LGPL, or RPGs. You only need to provide the plot, and some artwork if you wish, and ClanRPG will take care of everything else.
DataMonster is a console based application for managing data for d20 D&D games. Goals include monster generation, xp calculator, game time/calendar and combat manager.
Gnu Gaming Zone
GGZ (which is a recursive acronym for GGZ Gaming Zone) develops libraries, games and game-related applications for client-server online gaming. Player rankings, game spectators, AI players and a chat bot are part of this effort.
Gtkboard is a board game architecture and implementation. It implements all the common aspects of board games, such as the user interface, move parsing code, AI (i.e., game tree search) and file format.
gzochi is a framework for developing massively multiplayer online games.
i3dglload is a simple Innovation3d file loader. It renders the object with the OpenGL interface. The view is from a camera which can pan, zoom, and rotate around the object. It is mainly for game designers which uses Innovation3d.
IceUtils is a suite of command-line tools designed to make creating a game world and playing through that world an easier task. Although some of the tools are specific to Iron Crown's excellent Rolemaster role playing system, other tools can be used for just about any game environment in existance.
Illwinter Game Installer
The Illwinter Game Installer is an installer creator for Linux. All application files are compressed into a single linux executable making it highly suitable for web downloads. The Illwinter Installer is very easy to use both for the game developer and the end user.
M.A.M.E. Catalog/Launcher: consists of three programs: qmamecat (X11 version of the launcher; needs the Qt library), mamecat (text-only version of the launcher; needs a curses library) and catgen (a simple catalog generator)
Many Games is a system for creating and running a nearly endless number of user-defined (or downloaded) games in a graphical system. It will support games, such as checkers, tetris, solitaire, breakout, and almost any other two dimensional game.
The Massiv is a distributed game middleware whose purpose is to simplify the development of distributed persistent massively multiplayer online games. It is an object-oriented distributed system built on top of C++ and its standard library. It defines an "extended" object model, in a form of coding instructions, that allows the Core to fully manage application objects.
MegaZeux (MZX) is a simple but powerful game creation system. It currently officially builds on Windows (9x, 2k, XP), Linux (multiplatform), and MacOS X. Versions prior to 2.80 are available only for MS-DOS.
Momoko is an environment for building environments. It uses modular components and transparently distributes objects over multiple servers. It includes object-oriented version control and developing of environments from within the environments. Multiple languages are supported for writing object behaviours.
Open Gaming System
The Open Gaming System (OGS) is a platform for developing open gaming software. It defines a application programming interface (API) and provides a free software implementation of this interface. OGS is designed to be portable, reusable, and flexible enough for use in any game world or campaign setting including medieval, modern, futuristic, gothic, eastern, and western, as well as the traditional fantasy setting.
Open RPG Maker
Open RPG Maker is a free and open source 2D RPG creation utility, similar to the popular RPG Maker series.
QT AGI Studio
QT AGI Studio allows you to view, create and edit AGI games. Basically, it is an enhanced port of the Windows AGI Studio.
QuakeForge is a 3D graphics game engine based on id Software's legendary Quake and QuakeWorld game engine. Our purpose? To improve the state of the game by improving the engine and making it accessable to the largest number of players we can.
Rokugen is a Legend of the Five Rings Character Generator, written in Python/GTK+ and designed to run both in Win32 machines (Win2k and up) and GNU/Linux. It'll run on any computer that supports Python and has the GTK+ runtime.
Role Playing Database
(commmercial) Freeview Person replaces the typical 'messy' loose-leaf notebook typically used by Role Playing gamers to keep track of their characters, spells, monsters, tricks, traps, and worlds. The Role Playing DB implements a user-friendly GUI that presents representations of character, monster, spell etc. sheets as well as maps, using both hex and square spaces on the screen and saves the information on these sheets and maps.
VortexGE is a full software 3D renderer for the X environment intended for creating games under Linux without needing 3D card acceleration.
Xiqual 2D game project
Xiqual started out as a library of functions to make 2D games, with the goal of having at least some sprite functionality and tile map routines, plus a smattering of utility functions. It has since started to grow a bit beyond that, with the addition of CGI and net libraries and even an SDL GUI system making decent progress (bar some total redesigns).
Zune is a free clone of the famous MUI (Magic User Interface) toolkit from the Amiga. It is primarily designed for C, and uses BOOPSI as an object-oriented layer.