they have opened their site for the developers. Go and make your next generation VOIP application using flex + ribbit.
Here is the mail I have received from them:
Dear soon-to-be Ribbit Platform Developer,
Within the last 6 weeks, you filled out a request to download the Ribbit component and join our developer community.
We are happy to let you know that as of this week, the component has gone public beta and the developer platform is now open to all developers to join.
Join Now & Download the Component:
To join, go to: http://developer.ribbitphone.com/signUp.php
You will be approved and able to code within 24 hours.
You will receive a login username and password, as well as a dedicated purpose number to develop with.
You will receive 3 simple code samples to get you up and running, building your first voice enabled Flex and AIR apps.
You will be given access to our powerful and informative developer forums.
Happy coding and we can't wait for you to join our growing and valuable developer community!