HypeDyn (pronounced "hyped in") is a procedural hypertext fiction authoring tool for people who want to create text-based interactive stories that adapt to reader choice. HypeDyn is free to download and open source, and runs on Linux, MacOS and Windows.
The final HypeDyn 1 release is available here.
HypeDyn 2 0.26 beta (24 February 2017) is available here.
Experimental theme-based version from ICIDS 2016 is available here (MacOS X only for now).