Forum OpenACS Q&A: Re: webDAV Authentication Difficulties
"WebDAV Mini Redirector limitations:
•No support for HTTPS, i.e. no support for secure connections.
•Your WebDAV server must be using port 80, the default port.
•Typically fails when transfering larger files.
•Gets confused if the user does not have access to read and/or write to a file or directory."
So that kills it stone dead then. Even if digest authentication were to be implemented, you'd still want to use https, and you're very unlikely to want to do that on port 80.
How astonishingly mediocre!!