Re: FTP client to download file from "sftp over https"

I think you're crossing a couple of streams there. 

Here's the story on the elements you mentioned.

• FTP Voyager is SolarWinds free FTP client.  Windows users can use this to manually transfer files, synchronize folders or schedule transfers using any FTP, FTPS (SSL/TLS) or SFTP (SSH) server, including our own Serv-U FTP Server. 
• "FTP Voyager JV" (sorry about the name confusion) is an optional Java client for the HTTP/S interface of Serv-U MFT Server.  Desktop users can use this to manually transfer files or synchronize folders. 
• If you're looking to download content from a 3rd party website (i.e., not Serv-U) using https, I'd either use a utility like wget or double-check with the organization hosting the web site that they really don't have an FTP, FTPS or SFTP interface.  (Most commercial hosting companies do - if they do, then you may use FTP Voyager.)