Seems not to be that:

Notice: Undefined index: /kstars/downloads in /srv/www/svn/www/sites/edu/site_includes/class_handler404_edu.inc on line 56

Not Found

The requested URL /kstars/downloads/ was not found on this server.

I've searched the whole source code for strings http tycho2 usno and such, but didn't found where does kstars get all its extra data. Should I write directly to the developer?

The folder does exist, simply folder listing isn't permitted by the server.
See http://websvn.kde.org/trunk/www/sites/e ... downloads/ for a listing of the folder.

Many many thanks: finally found it (and in the sources too). I've sent the request to Debian and I'm in the packaging process.