Asterisk vs Kazoo

Asterisk is a free, open-source framework for building communications applications and turning an ordinary computer into a communications server. It powers IP PBX systems, VoIP gateways, conference servers, call centers, voicemail servers, and IVR systems. Listed functions include call routing, recording, queuing, conferencing, voicemail, automated attendants, and call transfers. Computer-telephony interfaces include AGI, AMI, and the Asterisk REST Interface (ARI); listed VoIP protocols include SIP, H.323, IAX, Jingle/XMPP, MGCP, and SCCP. Asterisk can connect communications to applications, including CRM systems through AMI. The source code can be downloaded, and the project points users to installation on a modern cloud Linux instance. Building applications requires working knowledge of Linux, scripting, networking, and telephony. Asterisk is distributed under GPLv2; Sangoma offers commercial licensing for uses incompatible with that license. The Asterisk forum provides community help with installation, upgrades, and operation.

Kazoo has no write-up on Specifiction yet; its figures are above.