GDevelop's runtime libraries are MIT licensed. It can be used freely for projects of any type and there are no royalties associated with publishing games developed with GDevelop.

The whole interface is intuitive and easy to learn: each part of the game can be designed using visual editors. The objects editor is used to create the objects of the game, the scene editor help you to build the levels of your game and the events editor allows to give life to the whole game without programming.

Prebuilt behaviors can be added to objects. This is a very efficient way to add a physics engine or make a platformer game. Lots of behaviors are included, from the most advanced (Physics, platformer, top-down movement) to really simple one (like the behavior to destroy objects when outside the screen or the one to drag objects with mouse or touch).
And you still have full controls over your game as behaviors can be modified using the events!