Godot Engine - Feature-packed 2D and 3D open source game engine.
Firebase - Firebase is a cloud service designed to power real-time, collaborative applications for mobile and web.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.
restdb.io - restdb.io lets you create databases and REST APIs quickly. Development databases are free. Powerful web-based and mobile-friendly data management.
Unity - The multiplatform game creation tools for everyone.
RemoteStorage - An open protocol for per-user storage OWN YOUR DATA