All major distros have rsnapshot already packaged. Here are a few links:
You can download the finished releases at http://rsnapshot.org/downloads.
All Versions prior to 1.4.0 are built by the maintainers manually and are only available over the rsnapshot-website.
Clone the git remote-repository at
$ git clone git://github.com/rsnapshot/rsnapshot.git
For installations-details consider the
Contributions of any kind are welcome. Open issues at our issue-tracker or bring pull-requests.