Wurfel Engine is a free and open source 2.5D isometric game engine written in Java. It was used for the development of the game Caveland.
Wurfel Engine is licensed under a BSD3 license which means you can use it for free - even commercially.
Runs on Windows, Mac and Linux.
Wurfel Engine uses algorithms specially designed for isometric block worlds and renders only what is visible to the player.
A powerful and efficient light engine shades the scene – vertex based or via normal map shading. Global and local light sources.
The map is divided into chunks which allows the streaming of almost unlimited world dimensions.
With the built-in WYSIWYG map editor players or level designers can shape an immersive world with immediate preview.
Download the Wurfel Engine SDK (containing source, jars, docs etc.):
Download Wurfel Engine SDK
For further information on the technology in Wurfel Engine article on Gamasutra or my bachelor thesis (German).