Luxinia is a highly scriptable 3D Game Engine that can be coded for by anyone with LUA. It doesnt require any compilers and comes with a API description. In the Engine package are various small test games that illustrate what can be done and how, as the sources are open as well.
Among many the key features are that you dont need to use fancy compiled code, but use relatives simple LUA scripts, material, particle or shader scripts to make your game. Once the engine was ported to Linux and maybe Mac OS X, the idea is that you make your gamepackage once and it will run on the other platforms without any further work of you.
Ease of use for simplicity and rapid prototyping were the goals for the engine. While it is not state-of-the-art, it does allow pixel and vertex shaders on modern cards and its powerful material system will work on older hardware too. The engine makes use of ODE for physics and collision, and also allows 2D physics for sidescrollers or jump'n runs.
There is a free license in the package, too.
The ProjectXmas Game let's you fly Santa over a little town and you need to deliver presents as quickly as you can. Part of game is also a simple Level Editor that serves as sample on how to make projects for luxinia. Another simple game included is a Space Shooter, a Bomberman Clone and some physics demos.
Visit http://strange-phenomenom.de/lux/ to find out more.