A Dynamic Update Client (DUC) is a program that redirects requests from a given URL to an IP address that is dynamically determined. This allows one to provide a fixed URL for an IP that changes. In some cases, the DNS host name of the IP will provide the same function.
That is not need with fusion, their propriety protocols handle the connections just so you don't need to do that.
So to answer your question, no you don't need to have a PC running all the time, have you setup your fusion account and registered the apex.