You can get fresh copy of the Railfrog reference application from the Subversion:
svn co https://svn.versiondude.net/railfrog/cms/reference_application/trunk railfrog_ref_app
Or grab Railfrog engine from the:
svn co https://svn.versiondude.net/railfrog/cms/railfrog/trunk railfrog
You can find installation guide in README file.