This is a member of the Viber :)
You can Install the app from the BlackBerry appWorld.
For more details you can check our help desk at: http://viber.kayako.com/Knowledgebase/Article/View/118/19/setup-viber-for-your-blackberry-device
If you have any question about Viber - please feel free to ask.
A member of the Viber R&D Team