Decker and Twine are very different animals, but they do have significant overlap: both tools make it possible to build interactive fiction in a largely drag-and-drop fashion, with little or no programming required.
I recently wrote an extremely rudimentary interpreter for Twine's .twee
format (I only support passages and one syntax for hyperlinks) just to see how difficult it would be:
You can try it out and rifle through the source code here: http://beyondloom.com/decker/goofs/minitwine.html
Would anyone be interested in a more elaborate elaborate writeup explaining how this works? Maybe with a slightly expanded featureset it could make a nice contraption.
EDIT: This prototype has now been superseded by the newer Twee Module