Duality is described as 'Modular 2D game engine / editor combo, written entirely in C# and built on top of an OpenGL backend. It's open source, features an open architecture that invites extensibility and technical ownership, and it embraces C# as a language rather than a scripting' and is a game development tool in the development category. There are more than 25 alternatives to Duality for a variety of platforms, including Windows, Linux, Mac, Android and Web-based apps. The best Duality alternative is Godot Engine, which is both free and Open Source. Other great apps like Duality are Unity, GDevelop, LÖVE and microStudio.
Limon is a multi platform 3D game engine mainly focusing on first person games. Focus of its development is ease of use and ease of study. It has builtin editor for maps, animations and GUIs.
Monkey is a modular language. You can create your own custom modules and use other people's - including the awesome box2d and minib3d modules!.
A unique combination of a powerful JS framework + an amazing set of authoring tools, WADE doesn't force you to do things one way or another - you are in charge!
