Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
ct.js - ct.js is a 2D game editor (desktop app) based on web technologies.
Ink by Inkle - ink is a popular open source scripting language for branching stories, designed for writers
PlayMaker + Unity3D - PlayMaker - Visual Scripting for Unity. Make games, VR, AR, and other interactive content in Unity without writing code.
Quest - Quest lets you create sophisticated text-based games, without having to program.
GDevelop - GDevelop is an open-source game making software designed to be used by everyone.