Viber is planning a version of the software for Windows and Mac and I got hold of screenshots for that.
The user interface of the Viber for Windows and Mac looks to be reminiscent of that of Skype’s, with a handy toolbar available at the bottom when using the full-screen video calling mode. The interface for the messaging view, however, looks similar to that of iMessage with two panes available for easy navigation.
It is unclear as to when will Viber release both version of the software. But given that they have already finished the development of the apps for Bada, S40, and Symbian, it is more likely coming in the next few months.