Wurfel Engine is an open source 2.5D isometric Java game engine used for the game Caveland.
Wurfel Engine is licensed under a BSD3 license which means you can use it for free - even commercially.
Windows, Mac, Linux are fully supported.
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.
Using chunks the map can be streamed.
Wurfel Engine uses a 3D world to build the world of your dreams.
With the build in WYSIWYG map editor players or level designers can shape an immersive world with immediate feedback.
Download the Wurfel Engine SDK (source, jars, docs etc.):
Download Wurfel Engine SDK
If you may be further interested in the technology used in Wurfel Engine, you can read my article on Gamasutra.