When Microsoft announced its purchase of Skype earlier this month, it took great pains to affirm its commitment to continuing support for the technology on platforms other than Windows.

Skype has decided not to renew an agreement that allows open-source telephony system Asterisk to be integrated with the service using software developed with Digium.

Cybercriminals have found a new launching pad for their scams: the phone systems of small and medium-sized businesses across the U.S.

The FBI has left users of Asterisk open source IP PBX products guessing whether the version they are using is vulnerable to a mysterious "new technique" that can be exploited by vishers - people who use VoIP to spoof caller ID numbers so victims will believe they are talking to legitimate businesses and give up valuable personal information.

Imagine an IP voice and unified communications system that can be integrated into any application and customised to meet business needs. Sounds great, right? Well that project is the Asterisk IP-PBX and it's free to use and you get the source code. A far cry from proprietary PBX systems perhaps, but Asterisk has a vibrant ecosystem and is replacing systems from more established telephony vendors. Following interviews with the leaders of the Horde and Free Telephony projects, the Open Source Identity series talked to Asterisk founder and Digium CTO Mark Spencer about how one application can have such a profound effect on businesses and how open source can be a tough competitive landscape.