Two big forces in the world of VoIP are coming together in a new solution called Skype for Asterisk (SfA).

The SfA solution, which entered general availability this week, combines the open source Asterisk VoIP PBX with the Skype VoIP network, providing benefits to both Skype and Asterisk users.

SfA comes at critical time for Skype, as eBay (NASDAY:EBAY) divests itself of majority ownership in its Internet phone unit. While ownership is changing, usage of Skype continues to grow, with 405 million users at the end of 2008.

"SfA is an add-on channel driver for Asterisk that leverages the power of Asterisk to route calls through the Skype community," Peter Engler, Digium's product manager for strategic products, told InternetNews.com. "A soft phone or hard phone would connect to an Asterisk PBX and the call routing in Asterisk would determine the route of a call, which could be over Skype, to a traditional providers service or any other avenue the administrator sets. All Skype features work transparently with soft phones being SIP or IAX clients."

Asterisk is a popular open source VoIP PBX that has been making waves in the market since its 1.0 release in 2004. The SfA solutions work with open source Asterisk versions 1.4 and 1.6 as well as the freely available AsteriskNOW application that includes a GUI and the Linux operating system. Commercial users of the Asterisk Business Edition will also be able to benefit from SfA. Not all Asterisk users will be able to use SfA, however.

Engler noted that SfA is not yet available for Asterisk hardware users on either the Digium AA50 or the 3Com branded versions. The Switchvox unified communication system, which uses Asterisk and is own by Digium, the lead commercial sponsor behind Asterisk, is not yet supported either. Engler said that Switchvox integration is on the roadmap, but a specific release timeframe has not been announced.

Asterisk itself is open source, but SfA is not.

"SfA is not open source due to the inclusion of proprietary Skype binaries and libraries," Engler said.

Digium has been talking about SfA since at least February of this year, and the product had an open public beta in August.

Engler said that close to 4,000 people signed up for the beta trial over the course of three beta phases. The first phase was a small group of testers, the next group was close to 100, followed by the open beta.

"The open beta allowed the 4,000 that signed up to try and report on SfA, of which close to 1,000 activated their license keys," Engler said. The beta users will pay $66 through the Digium Web store to get the full solution, Engler said.

While there were some challenges in getting Skype and Asterisk to work together, Engler said the teams from Digium and Skype worked well together to develop SfA, and with the assistance of beta testers, challenges were overcome relatively fast.

"The collaboration continues between Digium and Skype on the next release of SfA to add additional features," Engler said. "We are working and listening to our customers for these new features and priorities. Work will continue with the same Digium and Skype teams to bring SfA to the next level of functionality and solving problems for businesses."

The pending eBay Skype sale is not going to change the SfA roadmap either.

"The Skype sale from eBay does not affect Digium or SfA in any way," Engler said. "SfA is part of the Skype for Business portfolio of products, and the relationship will continue once Skype is an independent company."