Hello,
Yes, the module is in /experimental branch of CVS. Please take a look at README. You can authenticate, check groups and do few other things with Ldap using this module. It should work with Windows Active Directory as well. Pleae let me know.
However it was tested on SER 0.8.12x. I suppose it will not work on newest SER versions, because the sl module API was changed and I use sl_reply() there. Please see email from Jan Janak on Serdev list, dated 2006-03-01, subject "sl module api changed".
I see if I will quickly revise the module and test it with new SER versions soon. But I think it is maybe a better idea to start work on new Ldap db backend for SER, as it was discussed on serusers list before.