The differences between ns_register_proc on AOLserver and NaviServer are well described on the man pages, there are several places in the OpenACS where both AOLserver and NaviServer are handled - so no one has to be a "NaviServer expert" (whatever this is).
However, when starting from a version that is already broken, then "getting WebDAV" to work is probably by far a larger project than it might look like at the first glance. If the WebDAV code was not touched since 10 years, it probably needs various more changes and a lot of testing to work well on today's OSes. Handling of WebDAV was traditionally quite different under windows as it was under Mac OS X or Linux. Such a project should be probably done by someone having Windows on his desktop.
