Actually mhku I have managed to do it with my dm800 (but limited to only few channels depending the provider service).
I don't know if it can be done with the other models, needs testing and feedback.
The steps are very simple:
select the channel you want to stream, pass it through vlc.
Now here comes the limitation, depending the provider you are currently streaming only those channels can be opened as a second/third/forth..(so on)..
For example I watching Discovery world and at the same time I want to watch bbc knowledge, I stream Discovery world to vlc and then use different player (web interface) to stream bbc knowledge.
Also well streaming you can watch a different channel on your dreambox and record at same time.
To find out which channels fall under the same provider you need to stream a channel first to vlc, then open the channel servicelist in the dreambox, then each service will have a grayish/white color meaning its locked and cant be streamed, well the other services with a white in color means you can stream/record/view it at same time.
Best regards