I used Twine with the Sugarcube story format! It's open source and completely free to use. Also, for you and anyone else interested in getting into using Twine and creating your own games, there is a really good beginner's guide someone put together to help get you started (again, only for the Sugarcube format, I'm not aware of anything similar for Harlowe or other formats). They also have further Twine resources linked on the page as well.