Reality Factory - Reality Factory is a free suite of game development tools for building 3D games.
Godot Engine - Feature-packed 2D and 3D open source game engine.
CraftStudio - CraftStudio lets you craft games from scratch in real-time over the Internet.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
Limon Engine - Limon is a multi platform 3D game engine mainly focusing on first person games.
Unity - The multiplatform game creation tools for everyone.