As of now, while in Beta, it's totally free--and has been for about 5mo. That said, we are working on getting a free tier. Doing free as a startup when you have to have infrastructure on the backend is a little difficult.
Right now, it is free. You should give it a try. Within about 5min you will know if you like it or not.
Agreed. If it costs money to learn how to use a new PaaS, adoption will most likely suffer.
Part of what makes it so cool is that there is literally no learning curve. It's a pretty straightforward UI. We made that part of our goal when developing that platform: not having to relearn stuff to just deploy your app, like Amazon or Google.
Totally agreed, that's why ActiveState's Stackato (which also supports Java) has a free micro cloud. The Micro Cloud is a stand-alone instance of the Stackato system running in a single VM. This lets you push your apps to an environment that is functionally identical to a full PaaS cluster. ActiveState Stackato gives you 3 ways to test your application (1) on a Stackato Micro Cloud, (2) with an Amazon EC2 AMI or (3) on their Private Stackato Sandbox Service. check it out at http://activestate.com/cloud