That look like some variation of the Atreus keyboard from Phil Hagelberg, which I believe, he created around 2014 and in development ever since and quite popular amongst mechanical keyboard enthusiasts. Just ask Reddit. (There is now also a comercial version available on Kickstarter).
That one in particular looks like a Corne keyboard
I have been pondering myself about getting one instead of the ever elusive Textblade but haven’t done so for a couple of reasons:
1 - I REALLY don’t want all those wires but rather Bluetooth
2 - I have a MS Sculpt Ergonomic (MSSE) and I have yet to see a variation of the Atreus or the Corne that provide a design with the same kind of “wave”/curvature than the MSSE. I would have to design and print a case (which would also have to be VERY slim) to my liking (padded wrist rest, etc), which I’m not really in the mood for.
But the general idea that keyboards can have fewer keys and more layers is not new to the Textblade itself and has been explored multiple times in the past decades. Just look at stenography machines for instance.
What the Textblade (supposedly*) does very well is combine that functionality with multiple devices in a tiny package and thus why it is so attractive.
*I have yet to see one in real-life so I have to say that I’m talking based on assumptions that may not hold true and are based on the discussions here on the forum and Waytools’ description of the device