Very interesting, seeing that it is in Erlang also inspires confidence. I've been using another Erlang product recently, RabbitMQ, and the way you can just throw thousands upon thousands of messages on it, under heavy load, and it always delivers, no errors, no problems, amazes me.
Erlyvideo is also suitable for handling thousands of clients.
Is it possible to write a plugin that would stream audio not from a file but from some other source like a Unix socket, UDP socket, or a shared memory circular buffer?
Would that plugin be bound by GPL as well?
Yes, it is possible to create any plugin for erlyvideo and it must be GPL, because whole erlyvideo is GPL if you take it from github.
However, it is possible to contact me and receive code under other license.
This is a great project. It also does RTSP and M2TS/Apple Live Streaming.