What are some alternatives?
When comparing PlayN and GameMaker, you can also consider the following products
Unity - The multiplatform game creation tools for everyone.
Pygame - Pygame is a set of Python modules designed for writing games.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.
Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.
Unreal Engine - Unreal Engine 4 is a suite of integrated tools for game developers to design and build games, simulations, and visualizations.
CryENGINE - The most powerful game development platform is now available to everyone. Full engine source code.