Jake2 is a pure Java port of the Quake2 game engine. It features OpenGL rendering using jogl and OpenAL sound using joal. To use the Jake2 engine, you need either the data files from the original game or from the demo version. An online installation of the demo levels is possible. A lwjgl driver is included as an alternative to the jogl/joal combination. Single player and multiplayer modes are working. Jake2 comes close to the performance of the original engine written in C.
"The Game" is a project designed to simplify the process of producing any high-quality cross-platform 2D or 3D graphical computer game. The hope is that any game can be produced simply by changing a few settings and pressing a "compile" button. The project has three "deliverables": a game engine library to abstract across the set of all possible computer games (applying object-oriented design methods to the general problem in such a way as to be usable in specific instances); a graphical interface for easy game design (an exercise in human interface design); and a gaming package with a lot of shiny games to play.
Open Quartz is a project to supply artwork to create a full game based around the Quake source code. The pak0 module contains content (maps, models, graphics and sounds) and Quake code which controls the behavior and rules of the game. There is also a playable version available that ships with the Darkplaces engine by LordHavoc. The final goal of Openquartz is to become a 100% replacement for the original Quake game data that runs in all the free Quake engines available at present.