If his point was that PasswordMaker should prevent the editing of settings without entering a password, my response would be: how would PasswordMaker prevent someone from editing the RDF file on the hard drive, completely bypassing PasswordMaker?
It strikes me that this should be handled at the file system level. Store your RDF file in a user directory, for instance, so that other users can't edit it, or keep it stored on a remote filesystem (e.g,. over FTP or WebDAV) or on a thumbdrive.