Hello,
The plugin list is currently pointing to a dead project (2009?) which is not compatible with the latest roundcube version.
Some time ago, I've publish a project which support the latest version on github: https://github.com/northox/roundcube-yubikey-plugin . It would be great if an administrator could change the link on the Roundcube's website.
thanks,
I am assuming that you are talking about the plugin repository http://trac.roundcube.net/wiki/Plugin_Repository if so just create a account on the trac and change the link its an open wiki.
My bad, never thought about that.
thanks!