Man, this thing is confusing. Okay, I installed all three packages available in Synaptic, gsopcast, qsopcast and sopcast-player. I got exactly the same results you did, from all three players. The problem is all three have different dependency lists and none of the three list sp-sc-auth as a dependency or provide the binary, which is the key ingredient needed to play a sopcast.
darrel@AMD64: 55 items 636Kb -> apt-cache whatprovides sp-sc-auth
<sp-sc-auth>
nothing provides <sp-sc-auth>
darrel@AMD64: 55 items 636Kb ->Be aware that the following procedure is not "officially sanctioned" for support on the forum. But, in order to get one of the players to work, you have to copy one binary from outside the official repository sources. The binary comes from the SopCast website. Go back into Synaptic and completely uninstall all three players. Do this before anything else, or uninstalling them later wil erase the sp-sc-auth file you need to copy. Next, create an SOPCAST folder in your home directory, (NOT as root).
$ mkdir ~/SOPCASTThat isn't in any of the instructions I could find, but was displayed as an error when I first tried to launch sopcast-player. Next, go to
Sopcast's download page. Click the sp-auth.tgz download link and download it. Might as well save it to your SOPCAST folder. Here is the
direct link. Extract both files, sp-sc-auth and Readme. As root, copy sp-sc-auth to /usr/bin.
# cp sp-sc-auth /usr/bin/Don't forget the trailing
/. The Readme file contains instructions for installing libstdc++.so.5 library files. We are already using libstdc++.so.6, so you don't need the older ones. It also gives an example for playing an sopcast from the command line using an external player, such as VLC or Mplayer. It may also be used for broadcasting your own, from what I can tell. So, you may want to experiment with that later. But, installing the sopcast-player will be all you need for playback. So, open Synaptic again, and reinstall sopcast-player. After installing it, start the player from Video > SopCast Player or Internet > SopCast Player in the main menu. Once the player's on screen, click the orange SopCast Player Channel Guide button. You'll see a progress bar for building the database. You'll then see a list of channels. Open a category and double-click a channel to start watching.

If you know of any other sources for channel guides, please post them here.