RenPy - Ren'Py is a free and cross-platform visual novel engine that helps you use words, pictures, and...
Twine - Twine is an open-source tool for telling interactive, nonlinear stories.
TyranoBuilder - A Easy Visual Novel Development Tool!
Tuesday JS - Open-source, JavaScript engine for creating visual novels, interactive stories and text-based adventure games.
Ink by Inkle - ink is a popular open source scripting language for branching stories, designed for writers
SEEVN - Visual Novel Maker & Player