2Andi B.: I have access to yum repository via WebDAV, but not to the ftp. Anyway, VBox weights very much and I'm not sure if Netlabs' ftp has enough space to host the VBox builds archive. My ftp has enough space, so I'd better use it.
2Andreas Schnellbacher: yes, probably, I also need to activate access to the ftp via WebDAV. I have write access to yum repo, and the password is the same as Trac/SVN passwords are. But access is enabled separately, I think.