FusionPBX™ is an open source FreeSWITCH™ GUI. FusionPBX™ can be used as a high available single or multi-tenant PBX, call center server, fax server, voip server, voicemail server, conference server, voice application server, and a lot more. FreeSWITCH™ is a highly scalable, multi-threaded, multi-platform voice and pbx switch. FusionPBX™ license is the MPL 1.1 license.
It can be run on most operating systems on the hardware of your choice. It provides unlimited extensions, voicemail-to-email, music on hold, call parking, call center, call queues, analog lines or high density T1/E1 circuits and many other features. It provides the functionality your business needs and brings corporate level phone system features to small, medium and large businesses.