Godot is a fully featured, open source, MIT licensed, game engine. It focuses on having great tools, and a visual oriented workflow that can export to PC, Mobile and Web platforms
LÖVE is a open-source 2D game framework that uses Lua for scripting.
Flixel is an open source game-making library that is completely free for personal or commercial use. Written entirely in Actionscript 3, and designed to be used with free develo...