rsync hfsmode is a patch for rsync to enable recognition of Mac OS X HFS resource forks and Finder metadata, and to copy them to a remote filesystem. The destination system can be any OS and filesystem that supports rsync, so you can use rsync to archive Mac OS X files to servers running Linux, Solaris, et cetera.
In general terms, DeltaCopy is an open source, fast incremental backup program. Let's say you have to backup one file that is 500 MB every night. A normal file copy would copy the entire file even if a few bytes have changed. DeltaCopy, on the other hand, would only copy the part of file that has actually been modified. This reduces the data transfer to just a small fraction of 500 MB saving time and network bandwidth. In technical terms, DeltaCopy is a "Windows Friendly" wrapper around the Rsync program, currently maintained by Wayne Davison. "rsync" is primarily designed for Unix/Linux/BSD systems. Although ports are available for Windows, they typically require downloading Cygwin libraries and manual configuration.
"Last week, I told you about my NAS purchase, and my desire to explore desktop applications for backing up your Ubuntu computer. From the administrative interface of my Buffalo NAS, I created a network share that I could access with the different systems in my office. It's an SMB share so that it can also be accessed from Windows if needs arise. I then permanently mount those shares as network file systems (though not NFS) on my Kubuntu Karmic system. This I do from the command line