Here is another modern interactive fiction system of which I'm the creator and maintainer. It is fully opensource (BSD license): http://code.google.com/p/aetheria/
It can also parse sentences like the one with the sword and the wizard shown above. It's really not very difficult to achieve those things, as imperative sentences have pretty uniform characteristics that make the problem of parsing imperatives much easier than general parsing. As said in another comment, the bulk of the complexity of these systems is in the world model, not in the parsing.
A drawback is that, although the system works for several languages including English, the documentation for game developers/IF writers is only in Spanish at the moment. Collaboration for translating it to English would be very welcome.
It can also parse sentences like the one with the sword and the wizard shown above. It's really not very difficult to achieve those things, as imperative sentences have pretty uniform characteristics that make the problem of parsing imperatives much easier than general parsing. As said in another comment, the bulk of the complexity of these systems is in the world model, not in the parsing.
A drawback is that, although the system works for several languages including English, the documentation for game developers/IF writers is only in Spanish at the moment. Collaboration for translating it to English would be very welcome.