Babylon.js is described as 'Main features' and is an app in the Development category. There are more than 25 alternatives to Babylon.js for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and iPhone. The best alternative is Godot Engine, which is both free and Open Source. Other great apps like Babylon.js are Unity (Freemium), Unreal Engine (Freemium), GDevelop (Free Personal, Open Source) and CRYENGINE (Free Personal).
A game-engine fully integrated in Blender UPBGE is an open-source, 3D game engine forked from the old Blender Game Engine and deployed with Blender itself. This unified workflow is its main strength, as you can make your game from start to finish without leaving Blender.
GameplayKit is an object-oriented framework that provides foundational tools and technologies for building games in iOS, macOS, and tvOS using the Swift programming language and 3rd party rendering and multimedia libraries such as SpriteKit.