Game frameworks

Arianne / Marauroa Java, GPL-2.0, mature
Blender game engine C++, GPL-2.0, mature
COCOS2D-X C++, MIT, mature
Dash Engine D, MIT
Delta Engine C#, Apache-2.0
ENIGMA C++, C, GPL-3.0, mature
EasyRPG Player C++, GPL-3.0
Flare Engine C++, GPL-3.0
Flixel ActionScript, MIT, mature
GemRB C++, Python, GPL-2.0, mature
Godot C, C++, MIT, mature
HaxeFlixel Haxe, MIT, mature
Irrlicht Engine C++, C, zlib, mature
Lightweight Java Game Library Kotlin, C, BSD-3, mature
Lumix Engine C++, MIT, beta
LÖVE C++, zlib, mature
Maratis C++, GPL-2.0, experimental (4.x)
MonoGame C#, Ms-MPL MIT, mature
O.H.R.RPG.C.E Basic, GPL-2.0, mature
OGRE3D C++, MIT, mature
Octaforge C++, University of Illinois/NCSA Open Source License, mature
Open RPG Maker alpha, inactive since 2014
OpenFL Haxe, MIT, mature
OpenRPG Java, Python, inactive since 2013
Orx C, zlib, mature
Panda 3D C++, C, BSD-3, mature
Polycode C, C++, MIT, beta
Qt C++, LGPL, mature
Quad-engine Delphi, MIT, beta
SDL Game Engine 2D C, MIT, beta
ScummVM C++, GPL-2.0, mature
Solarus C++, GPL-3.0, mature
Superpowers Typescript, ISC
Urho3D C++, Angelscript, MIT, mature
Vega Strike C++, GPL-2.0, mature
WorldForge C++, GPL-2.0, mature
ZGameEditor Pascal, MIT, mature
jMonkeyEngine Java, BSD, mature
libGDX Java, C++, C, Apache-2.0, mature
mkxp C++, C, GPL-2.0
pygame C, Python, LGPL, mature
rpge C, GPL-3.0, beta, inactive since 2014
sandbox Game Maker C++, C, MIT, ZLIB modified (requires special credits and notifications)
xoreos C++, GPL-3.0