Why do I need this program when all macs come with a command line based md5?

Open a terminal and type:
md5 the-file-you-want-to-checksum

FTP is an obsolete and outdated protocol.
Anyone using FTP should seriously consider using WebDAV.

Since DAV works over HTTP, you get all the benefits of HTTP that FTP cannot provide. For example: strong authentication, encryption, proxy support, and caching. It is true that you can get some of this through SSH, but the HTTP infrastructure is much more widely deployed than SSH. Further, SSH does not have the wide complement of tools, development libraries, and applications that HTTP does.

DAV transfers (well, HTTP transfers) are also more efficient than FTP. You can pipeline multiple transfers through a single TCP connection, whereas FTP requires a new connection for each file transferred (plus the control connection).

Do a Google search for BarracudaDrive, which is an easy to use WebDAV server.
http://barracudaserver.com/products/BarracudaDrive/FileServer.lsp


You do not need a client if using Windows or Mac since a client is integrated into the operating system.