ioIsotope is indeed only available to registered users (foundation members in fact), but ioGui isn't. See
http://www.inicom.net/pages/en.ioftp...pts.php?id=108
I don't know any converter for serv-u userfiles. There are other converters so it shouldn't be too hard to get one to work with serv-u if you can provide details about the format of those files.