The repositories described at http://s3tools.org/repositories are VERY out of date. They have not been updated since January 2011. Worse still is that the download page (http://s3tools.org/download) RECOMMENDS the use of the repositories.
The version in the repositories is 1.0.0, however the latest non-alpha/beta version is 1.0.1.
I would suggest a recreation of the repositories into two types: a "s3cmd-GA" repo for General Availability releases (currently 1.0.1) and a "s3cmd-latest" for the most recent alpha/beta (currently 1.5.0-beta1). That way a user could choose to add either a repository that contains the latest well-vetted version or the latest experimental version.