Godot Engine
Godot is an advanced, feature packed, multi-platform 2D and 3D game engine. It provides a huge set of common tools, so you can just focus on making your game without reinventing the wheel.
Features
License
Godot is is completely Free and Open Source under the very permissive MIT License. No strings attached, no royalties, nothing. Your game is yours, down to the last line of engine code.