Gracie is an OpenID server (a "provider" in OpenID terminology) that serves OpenID identities for the local system PAM accounts. It authenticates users with a username/password challenge.
The OpenID protocol is documented at <URL:http://openid.net/>.
Gracie is free software licensed under the GNU GPL.
lists.tuxfamily.org/gracie-general
Gracie OpenID provider - General discussion
lists.tuxfamily.org/gracie-announce
Gracie OpenID provider - Announcements