For full functionality, I would have needed ActiveX. Still, I was able to configure RTSP, HTTP, and dnydns.org settings using Safari. Then I opened QuickTime and opened the URL of my webcam:
rtsp://MYHOSTNAME.dyndns.org/live.sdp
Instead of live.sdp -- which is the default on my camera -- you can choose any other name, as long as you don't forget the .sdp suffix. This might be useful, especially if you have more than one camera. As expected, the live video of my driveway opened in a seperate QuickTime window, thanks to dyndns from anywhere.
This hint might also be useful for those who want to watch live streaming only supported by ActiveX, but who don't have access to a Windows computer.

