The french title is "Utiliser des cartes à puce pour s’authentifier sur OS X Lion avec un OpenDirectory".
Yoann writes about the configuration of a Feitian smart card + OpenSC to login on Mac OS X Lion.
Yoann also improved the command line tool
sc_authto add OpenDirectory support (the command binary is provided but I can't find the corresponding source code).
sc_authis not a compiled binary but a bash script. So the source code is the program itself. I should have checked that before.