There are limitations, however: free calls over WiFi and 3G only work for supported OS versions, which is to say BlackBerry OS5 and OS7 – but decidedly not OS6, or at least not at this point.
Viber says this is “due to inherent limitations” of the OS, which powers devices like the BlackBerry Bold 9650/9700/9780, BlackBerry Curve 9300/9330, BlackBerry Pearl 9100 and BlackBerry Torch 9800.
Also not supported: BlackBerry 10, although I hear this may be the case when the final app gets rolled out in the near future.
It’s also worth noting that BlackBerry Messenger (BBM) was recently updated for devices running BlackBerry OS5, adding support for free voice calls over a WiFi connection, among other features.
But Viber says it differentiates from BBM because it lets users communicate for free, whether via voice calls or text messages, with users of all other Viber-supported platforms including iOS and Android.
The Israeli startup also just launched a new application for Windows Phone 8 that supports free voice calls.
Meanwhile, Viber boasts more than 175 million users worldwide. The company says BlackBerry users make up the third-largest chunk of its user base, after iOS and Android phone owners.
Viber is currently seeing 15,000 activations on BlackBerry per day.