All xowiki pages have a "name" and a "title". The "name" is a shortname that has to be unique per folder. xowiki supports page title since a few weeks and uses since this time title instead of names for labeling things. Since the language prefix is only part of the name, you should not bother about it.
It seems as if dave does not have currently the time to catch up with the developments in xowiki, so the installation of xowiki on oacs.org is quite old. dave uses a customized version of the category browser. Newer versions of xowiki come with a much improved category browser (much less sql queries, opens automatically the tree for a specified page, less jumpy on the screen, etc.), and some other includelets such as one for tracking recently changed xowiki entries similar to "recent posts" on the oacs start page, etc.
i would suggest to wait until the newer stuff is in place. It is quite simple to provide alternate category renders, e.g. by registering a mixin (the renderer is less then 20 lines of code). Currently, i am not sure, what the best way to display categories in a multi-lingual setup is, since the categories themselves have different labels, and once we have 10 or more languages, the flags might look silly.
