Hm, it uses an external copy of WinRAR... so you'll need both this copy + preferably a registered WinRAR version. WinRAR itself is a pretty solid piece of code, but I wouldn't recommend it for backup jobs as such - it does have some in-use-file support, but... meh.
For backing up my source code, I used to use two batch files. One for a weekly "full" backup, and one for a daily "incremental" backup.
FULL: c:\programs\winrar\rar a -os -tsm,c -agYYYYMMDD-HHMM -ac -k -m5 -md4096 -r -rr5p -s \\server\backup\source_full@.rar *
INCREMENTAL: c:\programs\winrar\rar a -os -tsm,c -ao -agYYYYMMDD-HHMM -ac -k -m5 -md4096 -r -rr5p -s \\server\backup\source_inc_day@.rar *
But IMHO, backup solutions that depend on a normal generic-purpose archiving software are going to have shortcomings of one form or another.