Swiftiply is on GitHub: http://github.com/wyhaines/swiftiply/tree/master. Check there for the latest code.
To download Swiftcore Swiftiply, go to http://rubyforge.org/frs/?group_id=3637&release_id=11668.
It may also be installed as a gem via
gem install swiftiply
The following links may be used as alternative download links: