melonJS is described as 'open source HTML5 game engine that empowers developers and designers to focus on content' and is an app in the Development category. There are more than 50 alternatives to melonJS for a variety of platforms, including Windows, Mac, Linux, Online / Web-based and Self-Hosted solutions. The best alternative is Godot Engine, which is both free and Open Source. Other great apps like melonJS are Unity (Freemium), Unreal Engine (Freemium), GDevelop (Free Personal, Open Source) and LÖVE (Free, Open Source).
Stencyl isn't your average game creation software; it's a gorgeous, intuitive toolset that accelerates your workflow and then gets out of the way. We take care of the essentials, so you can focus on what's important - making your game yours.
Cocos Creator is a complete package of game development tools and workflow, including a game engine (based on Cocos2d-x), resource management, scene editing, game preview, debug and publish one project to multiple platforms.
An open-source 3D/2D game engine for ObjectPascal. We support of lot of 3D and 2D formats (VRML / X3D, Collada, Wavefront OBJ, MD3, Spine...), we're portable to a lot of platforms (Linux, Windows, Mac OS X, Android, iOS...
One framework for creating powerful cross-platform games. The spiritual successor to XNA with 1000's of titles shipped across desktop, mobile, and console platforms. MonoGame is a fully managed .NET open source game framework without any black boxes.