Hmm,
The law on 'hacking' basically is obtaining information that is not known nor posted to the public. An ftp server can be construed as a private server through court systems if you are tried. But, if the files on the server are available for download, and could be downloaded by the general public, this means that there has been no steps that have exceeded gerneral knowledge to get to those files. In cruder terms, if you can not click through the web site to get to them, it can be made 'illegal' in the criminal justice system. {IE of something illegal is accessing the cgi-bin of a website, this could be on a website, but if there was not a link somewhere on the website to it, it is not "available to the general public".
But, IMO, if the filez are of use to you, I would download them and use them to the best of my abilities.