OpenUHS is a reader for Universal Hint System files. It's a game assistant that gradually reveals hints/images in a non-linear FAQ-like manner rather than spoiling everything as a walkthrough would. Over 500 games are known to the UHS repository.
Hypertale is a resource kit for working with interactive (non-linear)storylines. It can be used as a component for handling quests and other types of stories in e.g. adventure games, (MMO)RPG:s, or interactive fiction. It is built using Java and XML.
The 3D game development studio based on the Eclipse platform featuring modelling, non-linear animation of characters, scripting and deployment support.