Apps similar to UPBGE include Godot Engine, which is free and open source. Other options are Unity, Unreal Engine, GDevelop and GABE. You're spoiled for choice with Game Development Tools like UPBGE: we list more than 100 alternatives for Windows, Linux, Mac, Android and iPhone.
cocos2d-x is a cross platform open source free 2D game engine for mobile gamedev, that is fast and stable, easy to learn and use.
Verge3D is a powerful and intuitive toolkit that allows Blender, 3ds Max or Maya users to create immersive web-based experiences. Verge3D can be used to build interactive animations, product configurators, engaging presentations of any kind, online stores, explainers, e-learning...
Russia
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.
JoiPlay is a game launcher for Ren'Py, RPG Maker XP/VX/VX Ace/MV/MZ, TyranoBuilder and HTML5 based games
Phaser is a fun, free and fast 2D game framework for making HTML5 games for desktop and mobile web browsers, supporting Canvas and WebGL rendering.
United Kingdom
Torque 3D is a easy-to-use game creation platform. Architected from the ground up for maximum flexibility and performance across a wide range of hardware and built upon the Frontline award-winning Torque Game Engine Advanced, Torque 3D comes equipped with a full suite of tools...
United States
Adventure Game Studio (AGS) - is the IDE and the engine meant for creating and running videogames of adventure (aka "quest") genre. It has potential, although limited, support for other genres as well.
United Kingdom
Browser-based 2D game creation engine using a visual event-driven system, integrates JavaScript for advanced development, requires no installation or prior programming, supports exporting to HTML5, mobile platforms, Xbox One, and enables real-time editing on any device.
United Kingdom
United States
EasyRPG is a project aimed at producing a free and open source role playing game interpreter and editor compatible with RPG Maker 2000 and 2003.
Solarus is a free and open-source Action-RPG game engine, licensed under GPL v3, and written in C++. It runs quests in Lua, and can work on a great number of platforms. Solarus also features a game editor and a game launcher.
France
EU
An open-source 3D/2D game engine for ObjectPascal.
