Twine, a tool for telling interactive, nonlinear stories
You don't need to write any code to create a simple story with Twine
but you can extend your stories with variables, conditional logic,
Twine publishes directly to HTML, so you can post your work nearly
anywhere. Anything you create with it is completely free to use any
way you like, including for commercial purposes.
Twine was originally created by Chris Klimas in 2009 and is now
maintained by a whole bunch of people at several different repositories.