The only BUTT I'm aware of in this context is a streaming package called
Broadcast Using This Tool, which takes an audio input and turns it into a stream for Icecast or Shoutcast servers. It used to do that simple job just fine when it was my job to care about this stuff (and I'm glad to see it's still active and updated) but I'm not sure of its relevance to this thread. In any case, it's not a playout package, it is just a simple tool.