Free game engine for development of desktop, mobile, and web games
KorGE Game Engine. Multiplatform Kotlin Game Engine & Korlibs
Stride (formerly Xenko), a free and open-source cross-platform C# game
Cross-platform 2D game engine focused on ultimate productivity
Flax Engine, multi-platform 3D game engine
Vivid3D is a C++ IDE/3D engine, with python scripting.
A simple cross-platform game engine for creating old-school 2D games
PyCAPGE - Python Classic Adventure Point and Click Game Engine
Modified source engine (2017) developed by valve and leaked in 2020
Urho3D Game engine
A high speed C++17 Vulkan game engine
XNA based game engine completely written in c#
A cross platform 3d c++ game engine