PICO-8 - Lua-based fantasy console for making and playing tiny, computer games and programs.
Godot Engine - Feature-packed 2D and 3D open source game engine.
Moai - Moai is a spiritual successor to one of the elder gods of pixel editing: Autodesk Animator.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
Unity - The multiplatform game creation tools for everyone.