Torque 2D is described as 'extremely powerful, flexible, and fast open source engine dedicated to 2D game development' and is an app in the Development category. There are more than 10 alternatives to Torque 2D for a variety of platforms, including Windows, Mac, Linux, iPhone and iPad. The best alternative is Cocos2d-x, which is both free and Open Source. Other great apps like Torque 2D are MonoGame (Free, Open Source), AppGameKit Classic (Freemium), LibGDX (Free, Open Source) and nCine (Free, Open Source).
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.
SFML (Simple and Fast Multimedia Library) is a portable and easy-to-use API for multimedia programming. It is written in C++ with bindings available for C, D, Python, Ruby, OCaml, .Net and Go. It can be thought of as an object oriented alternative to SDL.
Allegro 4 and Allegro 5 are cross-platform, libraries mainly aimed at video game and multimedia programming. They handle common, low-level tasks such as creating windows, accepting user input, loading data, drawing images, playing sounds, etc.
Free and open-source, cross-platform 2D game engine written entirely in C# and based on MonoGame/XNA with additional features on top such as: content management (scenes, objects, variables, text, cameras) 2D physics pathfinding networking camera management scene...
AGKSharp is a free implementation of AppGameKit to be used with C# and .NET With AGKSharp you can write 2D and 3D application and games for Windows in an object-oriented language using the full power of AppGameKit, C# and .