Micropolis is a city simulation game engine based on the original classic SimCity source code. Micropolis is based on the Tcl/Tk version of SimCity. It consists of the micropolis module, which is the engine recast as a C++ class; the cellengine module, which is a cellular automata machine engine; and the tileengine module, which is a Cairo based tile renderer. It is intended to be used with the OLPC's Sugar user interface environment, but layered so the core code is useful in other contexts.
Arachnida is an embeddable Web server. It uses the OpenSSL library and consists of a small framework for networking that allows you to asynchronously accept and handle connections using a "new connection handler" to handle new connections and a "data handler" to handle incoming data. This makes it possible to add support for any TCP/IP based protocol by just adding a handler. A test suite is included.
Choerbaerts Suche nach dem Rönk (Choerbaerts search for the Rönk, or CSNDR for short) is the name of a 2d adventure. Its code is based on SDL and OpenGL. It is written in C++. At the moment, it is still under heavy development. There are playable releases available, but they are mainly for testing purposes without any story elements.
GNU FreeDink is a portable and enhanced version of the Dink Smallwood game engine. It aims at running the original game as well as its D-Mods (Dink MODules, or add-ons), with close compatibility, under new platforms. The internals of the engines are being cleaned up to allow for portability and later improvements.