freepbx - FreePBX is a web-based open source GUI that controls and manages Asterisk (PBX).
SlickText - Slick Text provides businesses and organizations with an easy and affordable platform for text message marketing.
FreeSWITCH - FreeSWITCH is an open-source media application designed to support popular protools such as SIP and WebRTC and provides a platform to develop voice and video applications.
SimpleTexting - SimpleTexting offers SMS and text marketing services for companies of all sizes.
Asterisk - An open source telephony switching and private branch exchange service for Linux.
Textmagic - The all-in-one solution for all your business texting needs - marketing campaigns, two-way SMS chats, reminders, notifications, and internal staff communication.