uvnc.com does have a linux version of the PcHelpWare repeater running, but there is currently a bug which makes it unreliable. Other Repeaters besides uvnc.com (3 so Far)
lists another public repeater.
In order to get the direct connection working when both machines are behind routers you need to port forward TCP traffic on port 5500 to the machine running the PcHelpWare_viewer and enter your public IP address or DynDNS hostname when the creating the server. In addition, you'll need to allow the traffic in any security software running on the viewer machine.