This is available from Install the Server. It adds server-side support for (:2column:) page directives and the paragraph continuation markup.
The subsequent paragraph is indented. Users of earlier versions can just download and install a new .xsl file.
The Wikibook server now announces its version number to the Splash Screen when invoked. However, upgrading the .xsl alone does not add this feature.
The 0.9.3 refers to the release number of the Wikibook DTD; the “c” denotes the server software fix level.