I'm happy to announce that as part of an ongoing partnership between the Wikimedia Foundation and PediaPress.com, PediaPress has agreed to release as open source a MediaWiki parser library written in Python:
http://code.pediapress.com/wiki/wiki
The library is released under a BSD license. It supports rendering mathematics and timelines, provided the correct dependencies are installed. It could be used for purposes such as offline readers or desktop applications.
Please contact the developers at mwlib <at> googlegroups.com if you have technical questions about the library.
-- brion vibber (brion @ wikimedia.org)