FrobTADS is a complete rewrite of the Unix console-version of TADS ("Text Adventure Development System"). It uses curses (or ncurses) and provides an interpreter to play games developed with TADS as well as the TADS 2 and 3 development tools. It adds support for a number of relatively recent user interface features including full support for text and background colors, TADS 3 banner windows, and timed input. It's also much more portable and more easily maintainable, as it's built to modern Unix standards.
Castle Game Engine is a cross-platform 3D game engine written in Object Pascal. It includes a flexible system of 3D objects, with out-of-the-box levels, items, intelligent creatures, and more. Rendering and processing of 3D models in X3D, VRML, Collada, and other formats is implemented. Many graphic effects are available, including shadows, bump mapping, shaders, mirrors, and screen effects.
Arx Libertatis is a cross-platform, open source port of Arx Fatalis, a 2002 first-person role-playing game developed by Arkane Studios. Arx Fatalis features crafting, melee and ranged combat, and a unique casting system where the player draws runes in real time to effect the desired spell. The Arx Libertatis source code is based on the publicly released Arx Fatalis sources. This does however not include the game data, so you need to obtain a copy of the original Arx Fatalis or its demo.
Fabula is a Python game engine suitable for adventure, role-playing, and strategy games and digital interactive storytelling. It offers a client-server architecture, an event-based protocol, multiplayer and networking capabilities, a multi-threaded server, an abstract, visualization-agnostic model of a game world, an asset manager, and a plugin system. Gameplay can be recorded and played back. The code is well documented and runs on Linux and MS Windows (it should work on OS X, too, but this has not yet been tested). Fabula can be used as a library to develop your own games. As an alternative, you can use the included Pygame-based graphical editor and the default game engine.
Click'n'Drag is a Python module that introduces the "Plane" class, which extends PyGame's "Surface" functionality, offering a hierarchy of mouse-sensitive, draggable Surfaces that can be used as sprites, windows, icons, or other interactive elements. In addition, the clickndrag.gui module uses clickndrag to provide basic GUI elements like container, label, text box, option list, and button.