Unlike UPnP, to have DLNA certification means you as a company have to pay for the approval, have the software/appliance go through a QC process, be validated, and voila. Then of course there are royalties for every unit sold with the DLNA sticker on the box...
At this stage in the 323's life cycle it isn't a viable option to become DLNA-compliant. It is easier to give the UPnP-AV server as many (or more) of those features and call it feature-complete.