There are 2 repositories under interactive-fiction-engine topic.
A browser-based text adventure game engine and sample game
Fractive is a free, open-source, Markdown-based hypertext authoring tool for writing interactive fiction.
Интерпретатор текстовых квестов URQ
Z-code engine for interactive fiction
An RPG-lite interactive fiction engine written in PHP
a C64 interactive fiction engine, with player also for Windows+Linux+Web
A Haskell-based interactive fiction engine
An object-oriented dynamic text-based interactive MUSH, or multi-user shared environment. Originally an experiment in object-oriented MUSH design, using database-hosted Python circa 2010.
An online fiction authoring tool for hyperlink and parser-based games