how to create a forum using ROR

A good discussion on creating a forum using ROR can be found in the
book "Beginning Ruby on Rails E-Commerce" by Christian Hellsten and
Jarkko Laine (Apress). There is a problem, however. The text
recommends the acts_as_threaded plugin to help with the forum
implentation. The issue is that the download location for
acts_as_threaded (http://www.railtie.net/plugins/acts_as_threaded.zip)
is not functioning. Does anyone know of an alternate download site for
acts_as_threaded?

http://i.nfectio.us/plugins/acts_as_threaded.zip

Thanks Stan!