For a list of released games built on FOSS game engines, SteamDB is a valuable resource. It provides details on games using various engines like GZDoom, Godot, Love2D, FNA, OGRE, and Torque. Additionally, many popular indie games like Undertale (GameMaker), Hyper Light Drifter (GameMaker), and Doki Doki Literature Club (RenPy) are built on open-source technology.