One framework for creating powerful cross-platform games
Open Source MMORPG Framework
A lightweight game server framework implemented with Actor Model
CTFs as you need them
Open source reimplementation of GTA San Andreas game engine in Unity
FiveM is a modification for Grand Theft Auto V
A Forge mod that implements SpongeAPI
JavaScript framework to build game engines, games, emulators and apps
A fast, scalable, distributed game server engine/framework for C++
Naval Robocode is a programming game for Java.
A game server framework in Go (golang)
C++ game libraries plus server.
Protect your Crysis2 server
Game framework on top of Python, Panda3D and Twisted