Open Source Game Engines

VASSAL is a game engine for creating electronic versions of traditional board and card games. It provides support for game piece rendering and interaction, and supports play by email or over a live connection.

DimensioneX is a free Massive Multiplayer Game Engine. It lets you develop and then run or host browser-based, graphical multiplayer games. The users will play games simply via their browser. DimensioneX runs on any Java-enabled web server (eg. Tomcat)

PyCAPGE (Python Classic Adventure Point and Click Game Engine) is a versatile, open-source framework designed for creating retro-style 2D graphic adventures using Python and Pygame. Inspired by the golden age of SCUMM games, it features a customizable 9-verb interface and robust inventory management. Key features include a Scene Manager supporting parallax scrolling, walk-behind masks, and depth-based character scaling. It implements intelligent Pathfinding to navigate complex environments automatically. The engine natively supports Multi-Character gameplay, allowing dynamic switching between protagonists. Developers can build rich narratives using the branching Dialogue System and a Cutscene Manager for scripted events. The architecture is data-driven: texts and definitions are separated into YAML files for easy localization. Includes a JSON Save/Load system and debug console.