Today, Asterisk deployments range from bicycle-powered embedded systems for wireless phone calls in Africa to enterprise call centre and VoIP service providers.

Locally, Asterisk users include prepaid calling provider AlphaNET, the US American Express help desk (served out of Brisbane), retailer Adairs, the University of Queensland, marketing company Clear Blue Day, and "a large Australian airline" that uses Asterisk for IVR to allow people to check the status of flights.

"The commercial impact is easy to show with high ROI, convergence of infrastructure, and an open door for unlimited innovation," Spencer said. "A lot of these things at the edge seem silly today, like paying for parking with your phone, but the future of VoIP will depend on features, not just voicemail and conferencing."

When asked how many people from outside Digium are contributing to the open source Asterisk, Spencer said the scale ranges from active participants to direct competitors that don't give anything back.

"Some resellers have staff who are active in contributing to Asterisk [and] in the middle you have a set of people who are contributing because of their own need, not because they are excited about telephones," he said. "There are a number of vendors that take Asterisk and produce products around it and contribute in a variety of ways, not just source code. A lot of people just take it as well and don't give anything back but also compete with us."

Spencer said open source projects need to convince customers to "work with you" and since there is a range of contribution levels from different people "you just have to accept it for what it is".

"Others like MySQL and Sugar[CRM] rarely receive substantive outside feature contributions [and] they use open source as a marketing tool," he said, adding Digium is working on a program to sponsor more core Asterisk developers."

CEO of local telecommunications analyst firm Market Clarity Shara Evans said Asterisk has proven to be popular with local ITSPs, with some 40 already using it to carry customer calls.

The AsteriskNow project is online at http://www.asterisknow.org/.