Blender Game Engine is described as 'The Blender Game Engine (BGE) is a component of Blender, a free and open-source 3D production suite, used for making real-time interactive content. The game engine was written from scratch in C++ as a mostly independent component, and includes support for features such as Python' and is a game development tool in the photos & graphics category. There are three alternatives to Blender Game Engine for a variety of platforms, including Mac, Windows, Linux, Blender and Web-based apps. The best Blender Game Engine alternative is Armory 3D, which is both free and Open Source. Other great apps like Blender Game Engine are Verge3D and Blend4Web.
Unlike BGE, Armory has not been discontinued. Armory, like Blender, is also open source, and also just like BGE, you don't have to leave Blender when you make your games.