Huge bump, but I think I found a solution to this: (I used the search if any of you already posted it, but I found none)
I got spotify to work on my Mede8er last week via JamCast.
and install it. It comes with a 2 weeks trial and after that you need to pay $20 once for a unlimited license.
After you installed JamCast, go to the server manager and click on the 'devices' tab. If all goes well you'll see a device called 'Realtek Embedded UPnP'. Press the rightmousebutton and enable 'Authorized for remote access' if it's not already enabled. Same goes for 'DRM playback permitted'.
Now click properties and set ForceMP3CaptureStream to True. That's all for now.
Start Spotify and start listening to a song. On the Mede8er, go to 'Choose Media' and press UPnP. In there you'll find a folder called JamCast. Go to Virtual Soundcard and you'll find a audio file also called Virtual Soundcard. Start playing it and after some seconds you'll hear Spotify music right from the Mede8er.
Because it's a kind of a stream, you'll always have a delay, mostly between 3-10 seconds.