An often requested feature for MCMS is to have the ability to use a custom autheticaton provider like Passport, AD/AM, LDAP or just a table in a SQL database. Although MCMS requires to have NT/AD accounts to be used for authorization it is indeed possible to use any 3rd party authentication provider you like for authentication!
How to do this is explained in the Custom Authentication section of the MCMS documentation.
In addition Spencer has provided a sample implemention for LDAP on his site (you need to search for LDAP and then click the link to expand the relevantsection).
The custom authentication link is broken. Would you know the updated link?
Just open the MCMS documentation installed on your MCMS server machine and search for "custom authentication".