Tramway SDK
Software library and tools for making the Tramway Drifting and Dungeon Exploration Simulator 2022 and similar applications. Similar to Quake, GoldSrc or Source engines, but it uses polygonal soup instead of BSPs and supports level streaming.
  MiniGDX
A minimalist Kotlin Multiplaform Game Engine
 
nCine
nCine is a cross-platform 2D game framework written in C++ with an emphasis on performance, but it is also scriptable in Lua for more flexibility. You can use it to create your games and tools or to learn and experiment with its source code.
 
Stencyl
2D game engine written in Haxe, with a block based visual scripting system inspired by Scratch
 
Echo Engine
Echo is a game engine which uses many industry-standards for game development
 
Pixelbox.js
A combination of an editor and a simple JavaScript library to create game without the cumbersome aspects of HTML5 development
 
Cocos2D-X
A multi-platform framework for building 2d games, interactive books, demos and other graphical applications
  Welder Engine
A cross platform game engine that can be used to make simulations of any kind, ranging from simple prototypes to professional 2D and 3D games, simple physics or graphics demonstrations to robust, realistic simulations.
 
Superpowers
Free and opensource 2D+3D game making for indies
 
PX8
Lightweight fantasy console for making retro inspired games
  rot.js
A set of JavaScript libraries, designed to help with a roguelike development in browser environment
  AllBinary Platform
AllBinary Game Engine is a multi-platform game engine in Java. Entire game engine is also in 100% Kotlin. Supports: Android (Without native libraries in Java or Kotlin), HTML5, J2ME (MIDP), Windows Native (Avian), and J2SE (Java or Kotlin).
 
Bitsy
A little engine for little games, worlds, and stories
 
Clickteam Fusion 2.5
Battle tested 2D game engine with an accessible visual scripting system
 
CopperCube
A complete 3D authoring tool which includes all the features you need for creating games for multiple platforms
 
Core Engine
C++ Coding Framework for Windows, Linux, macOS and Browser games
  DungeonScript
A variant of Puzzlescript featuring 3D graphics, a first person perspective, and no limit on 2D pixel and 3D voxel sprite resolutions
  Easel
Easel lets you code multiplayer games without coding the multiplayer. Code like all your players are in one shared world, like a singleplayer game, and Easel does the rest.
  Easy RPG
EasyRPG is a community project to create a free, open source, role playing game creation tool, compatible with RPG Maker 2000/2003 games.
  EngineLol
An experimental web-based Game Engine to create simple interactive fiction
  Esenthel
"Esenthel" is a mix of words: Essential and Essence, with a touch of magic
 
Evergine
The graphics development engine for business and industry
  Flickgame
Flickgame is a game-/story-/thing-making tool. You have sixteen frames, sixteen colors, a few brush sizes, and the means to link together frames via the color menu.
  Isogenic
HTML5 2D and isometric scenegraph-based game engine written entirely in JavaScript
 
KaboomJS
A Javascript game programming library that helps you make games fast and fun.
  luxe
An easy to learn game engine for making 2D or 3D games. It prioritizes design and workflow for rapidly expressing ideas.
  Macroquad
A simple and easy to use game library for Rust programming language, heavily inspired by raylib.
  Microsoft MakeCode
A free online learn-to-code platform where anyone can build games, code devices, and mod Minecraft
 
Next2D
An engine that provides a WebGL 2D rendering, a web authoring tool for animation production, and a framework to support team development