Ductus is a wiki system designed to handle arbitrarily-structured content and a variety of workflows. It is free software licensed under the GNU GPL version 3 or later. Currently it is used by the Wikiotics language instruction project.
With Ductus, programmers can easily define classes of structured content, providing rich mechanisms for user interaction. For instance, Wikiotics allows people to collaborate on "language lessons," which can later be used as quizzes or flashcards. Such modes of interaction are not possible with most wikis which are designed primarily to handle freely-structured text.
More information is available at http://code.ductus.us/
Installation/bootstrap instructions are available in ductus/doc/install.rst