Godot Engine - Feature-packed 2D and 3D open source game engine.
GoodBarber - GoodBarber is a mobile app creation platform.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
Fuse - Fuse is a UX tool suite for mobile app designers and developers.
Construct 2 - Scirra Construct is a 2D game development engine with a focus on building games visually.
Dropsource - Mobile development platform for building native iOS & Android apps