The NDS product from Novell is the one to aim for not that bastard of standards called M\AD. NDS has better functionality and it does better conform to standards.
When you produce an innovative use of NDS, you can get a license from Novell to use NDS for many users in your product. This does not exclude OS products !
Novell has a tradition helping Open Source projects like OpenLDAP and it is currently hosting projects. They contributed crucial technology to kick-start things and they provide software and open standards to the community.
IBM's directory server 4.1 is available at no cost.
OpenLDAP is since 20030410 available in the stable 2.1.17 version.
Conclusion, the functionality in the article refers to is needed and to some extend available, but AD is not the role model here, NDS is.