The website notes the project is in its early stages. So it's either in "ideas debating" mode or "vapourware" if you want to be less generous.
House building is already open source: all the information is out there in your local public library / on the internet. Nothing is closed to you in the way that you can't look inside some proprietary software to understand what's going on. If you have the time, you can read up on everything from applying for the legal permissions to put up a house, designing a building, and all the way through to finding out how to dig trenches, run electric cables and paint walls. Nothing is closed from you (certainly in the majority of countries in the world).
There are choke points: the expense of hiring architects, specialised builders, legal advisors. None of these are closed to you. What you are doing is saving the years it takes to learn these trades and paying somebody else to do these tasks because its quicker, so more efficient for you in energy terms. There is a small but consistently strong movement in many countries of people who already build their own homes, where they have made the choice to give up their jobs as computer programmers/nurses/rangers/whatever and spend several hundred hours digging trenches, laying brickwork, drawing architectural diagrams etc. It's already open source.
I think what these people might be doing is trying to shortcut the architectural expert choke point and break architects' hold on construction. But at the end of the day if you want a self build house, you're still going to have to go up a ladder and move heavy things around a lot and deal with construction elements that need careful attention, like mains electricity, water piping and gas.