AweMUD is a MUD server for use with fantasy-settings. Features include fully dynamic objects and characters, an advanced scripting system, and custom worlds. The engine will eventually have completely interactive rooms (items can be placed under benches, doors can be destroyed), complex magick, and interactive NPCs.
BZFlag is a 3D, multiplayer, tank battle zone, capture the flag game that pits players against each other in a networked environment. It runs on Windows 95/98/NT/2000, Linux, MacOS 10.x, Irix, Solaris, and others. An OpenGL accelerator is highly recommended, but it is playable with 3D in software.
ClanLib is a cross-platform game SDK currently supporting Windows and Linux. It provides easy-to-use interfaces for 2D graphics, input, sound, resources, networking, GUI, OpenGL, and more. The goal is to provide a game SDK that does all the dirty work that all modern games need to implement anyway, thus making the game developer concentrate on the gameplay instead of reinventing the wheel over and over again.
GCompris is an educational software suite with numerous activities for children aged 2 to 10. Some of the activities are game-orientated, but nonetheless still educational. These include computer discovery (keyboard, mouse, different mouse gestures), algebra (table memory, enumeration, double entry table, mirror image), science (the canal lock, the water cycle, the submarine, electric simulation), geography (place the country on the map), games (chess, memory, connect 4, oware, sudoku), reading practice, and others (learn to tell time, puzzles of famous paintings, vector drawing, cartoon making, etc.). It currently offers in excess of 100 activities, and more are being developed.