Asterisk, the world’s most popular open source communications project, is free, open source software that converts an ordinary computer into a feature-rich voice communications server. Asterisk makes it simple to create and deploy a wide range of telephony applications and services, including IP PBXs, VoIP gateways, call center ACDs and IVR systems.
Asterisk is released as open source under the GNU General Public License (GPL), and it is available for download free of charge. Asterisk® is the leading open source telephony project and the Asterisk community has been ranked as a key factor in the growth of VoIP.
Certified Asterisk is a branch of Asterisk supported by Digium for commercial and SLA customers, entitled under certain Support offerings. Like other branches of Asterisk, it is provided under GPLv2 license and may be used freely by anyone, even users and other customers who are not Digium’s SLA customers.
Interested in Commercial licensing? Asterisk is distributed under a dual license: an open source license, and a commercial license. The open source license under which Asterisk is distributed is the GNU Public License version 2 (GPLv2). The GPL is the world’s most popular open source software license, currently used by nearly 50% of all open source software, including such software as the Linux operating system kernel, the Firefox web browser, and the MySQL relational database management system. For many people, the GPLv2 license suits their use of Asterisk completely. These users are not distributing proprietary modifications, additions to, or derivatives of Asterisk and they do not require the legal protections of a commercial license.
For others, the GPLv2 might not suit their use of Asterisk. When users want to use Asterisk in ways, products, markets or have other requirements that are not compatible with the GPLv2, Digium offers commercial licensing of Asterisk.
Software add-ons for Asterisk are available from Digium and through other vendors. You’ll find popular add-ons and third-party apps that extend the power of any Asterisk open source configuration. If you are looking for speech to text applications or other vendors who have created applications to add value to your Asterisk installation, you’ll find options with Digium software add-ons.