Digium has released the latest version of its free and open source VoIP software Asterisk.

Now her computer's Skype software—which makes possible free phone calls via the internet—rings and “Vera”, sitting in Shanghai where it is late morning, says Ni hao to begin the lesson.

But as handsets start to resemble pocket computers, with downloadable games and other software, the threat of mobile VoIP looms ever larger.