I don't know much about patents, but my understanding is it's a win32 build that uses the cygwin dlls to provide some of the linux functionality in a windows environment, but doesn't need all of cygwin installed.
I've zipped up (and changed the password :) ) of the rsync folder I use with backuppc at
http://digdilem.org/misc/rsyncd.zip service.bat installs rsyncd as a windows' service and the default share is all of c:\ (protected by a user/pass) on the standard rsync port - and any rsync client can then connect and copy exactly as you would a linux server. It works well and is very lightweight, and being rsync is efficient in what it copies. No other software is needed in Xp, Vista or Win7, although if windows firewall needs to stay on obviously rsync's port needed opening.
I also normally include a win32 build of munin-node in that folder, which gives some very basic stats for my pretty graph factory...
Si
