I have no problem actually running it with Media Player (even in fullscreen, with the proper command line option). I am using this with one of the screensaver "fakers", which launch Media Player after specific idle time. However, this has all the disadvantages of not running proper screesaver, i.e. I have to close the window manually when I get back to work, some events from other applications get on top, etc.
Therefore, I hoped there might be an actual screensaver that would display streaming video. That is, there is one I mentioned at the top, but it is not working...