I'm not sure what this website does. It doesn't seem to provide anything concrete, except for the faulty premise that low adoption of home automation is due to a lack of interoperability between vendors, and the proposition to fix that by sprinkling some magic 'REST API' dust on it.
People who decide whether to buy a home automation system or not don't give a flying fuck about interoperability - they want one vendor to install and maintain it for them anyway. What they care about is cost, features and (for renovations) how hard it is to install the hardware, and how much it can do for the money and time invested.
What we need is more accessible hardware, not more software. There is plenty of open source home automation software. What we need are cheap ways to build sensors, buttons, actuators etc, plus a cheap way to make them look good, too (that last part is the hardest, actually).