Whisper reminds a lot of the other social networks we all have seen. You write your status updates in your news feed, and your friends will see them in their news feeds. You can write things in yours and your friends logs, make comments and so. Not much new here.
The revolutionary concept of Whisper is beneath the surface. There are no servers! Or, all participants in the Whisper network run the servers, depending on point of view. When you are communication with your friends, you are doing it directly, friend-to-friend. By accepting a new friendship, you are at the same time accepting to assist this friend with storage and distribution of his or hers information.
The Whisper software is freeware.