A D(istribution)KDM is a KDM. There is no difference between the two.
DKDM is a term used when a KDM is intended for another postproduction entity instead of theaters. For example, when a laboratory wants to deliver encryption keys to another laboratory that creates, rewraps or unwraps DCPs and their encrypted content.
The Recipient (in AuthenticatedPublic > RequiredExtensions) will be set to another encoder (such as DMS2000) instead of a DCI player in a theater.
To learn everything about DKDM, simply read the KDM chapter :)
