Eclipse Origins was create using Mirage Source as the foundation. It's written in Visual Basic 6, and while that has been proven to run on both Windows 11 and Windows Server 2019, it's incredibly outdated. Try MirageBasic instead, which is a VB.NET conversion of the Eclipse Origins source code.
PlayCanvas - PlayCanvas is an open-source game engine built on WebGL and WebVR.
Spring Engine - Spring is a versatile 3D RTS game engine.
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
FIFE - FIFE engine - open-source multi-platform isometric game engine
Flare (game) - Flare (Free Libre Action Roleplaying Engine) is a simple game engine built to handle a very...
Sacred - A shadow of evil has fallen on the kingdom of Ancaria.