I have some experience with ffmpeg's ffserver. The project is abandoned by the ffmpeg team but I'm still running a setup that can do webm livestreaming with relative ease. I've only messed with the mp3 option a bit but it would be doable to pipe audio (youtube-dl) to ffmpeg -> ffserver.

The biggest problem with ffserver/mpd over more traditional shoutcasting services is you'll have no option of adding another source (i.e. a mic for the dj) short of mixing those 2 sources locally and then streaming them off to ffserver/mpd.