DDUP is a program to update DNS servers like DynDNS with your dynamic IP. Visit www.dyndns.org for more information on this service, or www.ddup.org for more information about this tool.
Tobias Ernst has ported the new version 3 (which is required for DynDNS now, the old version 2 which you can find on Hobbes will no longer work) to OS/2.
Source: OS/2 ORG