I’m doing a little literature study related to P2P networks, and found, to my surprise, that there has actually been some research on DC. Here’s a list of publications that I’ve found on Google Scholar:
SS Gupta and S Rajagopalan, “A measurement-based study of the Direct Connect Network”, 2007. PDF
I. Bica and A. Furtunã, “DC++ and DDOS Attacks”, 2007(?). PDF
This reads like it was written as an assignment for a bachelor course. Not of particularly high quality, but an interesting read nonetheless. (I chuckled at the “Nowadays it is being maintained and developed by various groups from the Internet.”. Don’t worry, I’m from the Internet!)
K. Molin, “Measurement and Analysis of the Direct Connect Peer-to-Peer File Sharing Network”, 2009. PDF
Master Thesis, so somewhat more elaborate than a paper.
A.J. Alberts and A.S.J. Helberg, “Practical Implementation of a Virtual Currency Based Incentive Mechanism in a Direct Connect Peer-to-Peer System”, 2010(?). PDF
Unfortunately, it doesn’t seem like any of the above publications have been submitted or included in a journal. But they still make for a quite interesting read.