http://en.wikipedia.org/wiki/Direct_Connect_(file_sharing) lists a couple of applications that support DirectConnect protocol. Amongst those are at least 3 native mac clients:

 - MLDonkey http://mldonkey.sourceforge.net/Main_Page 
 - ShakesPeer 
 - Jucy 

 
None of those, maybe with the exception of MLDonkey, seems to be very actively maintained though. I would have loved to post links to the other two too, but stack exchange won´t let me ;-)