Free, cross-platform 2D game engine powered by Haxe and OpenFL
New Godot bindings for Swift
Open source library for creative expression on the web, desktop, etc.
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Urho3D Game engine
online 4X browser game engine
The Atomic Game Engine is a multi-platform 2D and 3D engine
2D physics engine for games