SEMS is a GPLv2+ media and application server for SIP based VoIP services. Basic applications like announcement, pre-call announcement, RBT, conference, voicemail, mailbox etc. and lots of example applications available.
RadioBox is open-source broadcasting solution that relays on client-server architecture. It consists of media server that runs as a service and listens for socket connections of graphical interfaces (web access, Windows GUI, Linux GUI, etc...)