A free/open source client and automation tool for Ragnarok Online
The ioquake3 community effort to continue supporting/developing id's
ThinkPHP Framework
Flexible level editor
Open-source rhythm game
Fast PlayStation 1 emulator for x86-64/AArch32/AArch64
An iOS & tvOS Frontend for Multiple Emulators
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
RetroArch is a frontend for emulators, game engines and media players.
Fast, user-friendly cross-platform custom launcher for Minecraft
Cross-platform 2D and 3D game engine with modular architecture
Source code repository of the FreeOrion project
CTFs as you need them
3D and 2D game engine written in Rust
dhewm 3 main repository
DeSmuME is a Nintendo DS emulator
A fancy self-hosted monitoring tool
Stride (formerly Xenko), a free and open-source cross-platform C# game
Mangos ZERO is a server for World of Warcraft
Free game engine for development of desktop, mobile, and web games
C# application with primary purpose of farming Steam cards
API and runtime that allows access to VR hardware
Voxel game engine in C++ with OpenGL
Free and open source real-time strategy game
The Tiny JavaScript Game Engine That Can!