I think you are getting a few things mixed up: voctomix has nothing to do with stream/video hosting, and is a different part of the stack.
Yes, the website (media.ccc.de) is https://github.com/voc/voctoweb/, but live streaming is actually a differennt project: https://github.com/voc/streaming-website
They do interact a bit, to make it seem more seamless.
Peertube is well suited for events like FOSDEM. The CCC use https://c3voc.de/wiki/voctomix but a littler harder to use.