My understanding of ADFS is that your responsibility ends at trusting other organizations, not individual users. The users are users in the AD's of the other organizations (or whatever else they use - it is not limited to Windows AD). User management falls outside of the portal's realm and into theirs. That way, when a portal user leaves a job and their employer closes their account in their domain, they can longer access the portal. It saves users employers having to remember to tell you that Fred Jones no longer works for them or has changed job function and so should heve his rights on your portal revoked. It all happens automagically.

In answer to your question, I do not beleive that the DNN AD module has much, if anything, to do with ADFS because the users are not members of the domain (AD) in which the portal operates. ADFS would authenticate users from other companies, not your own.

ADFS is for not normally for use within a single company. It is usually allows company A's web app to allow Company B handle all user account details for itself. That of course is a huge simplification. You best bet would be to start here:

http://msdn.microsoft.com/msdnmag/issues/06/11/SingleSignOn/default.aspx

It give a good idea of what ADFS is and what it is used for.