Unity3D Client And C# Server Framework
One framework for creating powerful cross-platform games
A simple and easy-to-use library to enjoy videogames programming
lua dev plugin for unreal engine 4 or 5
Open Source MMORPG Framework
Desktop/Android/HTML5/iOS Java game development framework
CTFs as you need them
Gideros Release version
A game framework written with osu! in mind.
Self-hosted CMS platform based on the Laravel PHP Framework
You can make it - Open Source MMORPG Platform
Arianne is an engine to develop multiplayer online games like Stendhal
JavaScript framework to build game engines, games, emulators and apps
Amateur 3D Game Engine
Examples of procedural geometry for Unity3D C#
Game engine supporting many 3D/2D formats and graphic effects
Orx: Portable Game Engine
PyCAPGE - Python Classic Adventure Point and Click Game Engine
Molecular viewer and prototyping framework
Vivid3D is an open-source 3D engine with powerful 2D UI.
Java Settlers
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Modern 3D engine and IDE written using C# and C++.
8-bit Graphical API for Java