It will be MIT licensed, the flat file data will be exportable to JSON and RSS. Our app's core will be quite similar to Pico (http://pico.dev7studios.com), so have a look over there if you already want to get an idea of how theming will work (of course the rest will be different :)
Skrive is an early stage Open Source Project that aims to make web publishing easy for both client and developer / designer. Skrive will be free to run on your own server using PHP. More info about the tech over here: https://medium.com/im-skrive/bd5ac719c704
Most sincerely,
Laurens