Have to confess I am a big fan of Alan Kay and Bret Victor - hence the links in the welcome message.
This project at first glance seems a little peculiar - why are they using paper instead of screens, aren't screens more dynamic? This is why I think they've gone down this path:
2) They need a public exhibition / collaboration space in order to fundraise and get the word out, since their Y Combinator Research money is coming to an end (I think). This gives them long term viability with any luck.
3) Bret was really
tired of screens and wanted to demonstrate the latent social potential of computing with even meagre means.
In terms of 'practical details' or current lack thereof, I think their motivation is to prototype designs now that can guide applications of future technologies that are more dynamically capable. And once those technologies arrive I think their goal is to be
first in line to show off the potential.