While big business may be crowning open source as the king of server-based computing, most enterprise movers and shakers vehemently deny any such moves in telephony. Yet, open source in telecom is long past its debut and is, in fact, already in play in much of the Fortune 500. So why is open source a legitimate option in enterprise computing but bastardized so much in telephony?

Linux company DcData and telephony solutions providers BizCall have entered a strategic partnership in order to provide IP telephony and Voice over IP (VoIP) services to the Kwazulu Natal market, forming BizCall KZN.

Asterisk bills itself as "the world's leading open source PBX, telephony engine, and telephony applications toolkit." You can use it as the basis of a fully featured, enterprise-class phone system in your organization.

Building Telephony Systems with OpenSER is a new book from Packt, which acts as a step-by-step guide to building a high performance Telephony System. Written by Flavio E. Goncalves, this book teaches users how to develop a fast and flexible Session Initiation Protocol (SIP) server using OpenSER.

skAsterisk, a PBX, telephony engine, and telephony applications toolkit, is one of open source best-kept secrets. As with many open source projects, there is a company that has been set up to provide support, Digium.

Here's its latest press release:

TapRoot Systems is demonstrating its telephony middleware for Linux/Qtopia-based mobile phones at the Linux Mobile Communications Conference this week in Beijing. TapRoot's director of product management, stated, "Development of Linux mobile phones is on the rise and is changing the landscape of the mobile phone industry. Our LinuxTel telephony software is a critical piece."

Move over proprietary telephony systems. Australian engineer David Rowe started the Free Telephony Project three years ago to build an affordable IP-PABX system out of free hardware and software.

In addition to the well-known Asterisk, there is a vibrant community of open source software PABX systems that can be used for internal and service provider IP telephony.

As IP telephony gains acceptance in the SMB market, it's not likely to be the products of mainstream IP PBX vendors that lead the change. Open source software, some say, may be the mechanism whereby IP telephony vendors bring affordable, reliable, and innovative products into the largely untapped—and highly cost-conscious—small-business arena.