Mindustry
Factorio-like tower defense game.
Lila
Ad-less chess server powering lichess.org, with official iOS and Android client apps.
Luanti
Voxel game engine (formerly Minetest).
OpenTTD
Transport tycoon simulation game.
The Battle for Wesnoth
The Battle for Wesnoth is an Open Source, turn-based tactical strategy game with a high fantasy theme, feat…
MTA:SA
Add network play functionality to Rockstar North's Grand Theft Auto game series, in which this functionalit…
Hypersomnia
Competitive top-down shooter blending Counter-Strike with Hotline Miami.
Razzia
Quiz game platform, designed for smaller self-hosted events (alternative to Kahoot!).
Zero-K
Open Source on Springrts engine.
DDraceNetwork
Cooperative platformer version of DDRace, a Teeworlds modification featuring unique cooperative gameplay.
Scribble.rs
A web-based pictionary game.
Red Eclipse 2
Arena first-person shooter similar to Unreal Tournament.
Suroi
An open-source 2D battle royale game inspired by surviv.io.
piqueserver
Server for openspades, the first-person shooter in a destructible voxel world.