Don't understand why they didn't just make an iPad mount. There's plenty of software to extend your desktop remotely. A small display like this doesn't need to be able to run high frame rate games.
Have you watched the video, he explains why he decided to build it that way.
I would not be surprised if this is literally replacement iPad screens with markup. iPad screens use a form of DisplayPort internally.
Yes, it's the same display as an iPad. Pretty sure he mentioned that in the video. I'm glad someone is doing this commercially. I hoped someone would since I first saw this DIY project last year: http://emerythacks.blogspot.ca/2013/04/connecting-ipad-retin...
I don't see the issue with calling it small. Small and large are sizes, whereas resolution is a quantity independent of size. A 9.7" screen is small, whether it's 1x1 or 2048x1536 or 4096x2160.
Even if I have a 10" display, I don't want my computer effectively transcoding video all day, degrading my wifi connection, and my iPad to have 5 seconds of latency making it impossible to see what I type. If the client and host have hardware to handle the resolution on-chip (upscaling/downscaling or compression/decompression), then that's a fair statement. To be fair, this might be the case. Regardless of the physical size of the display, it sets off reliability alarm bells to say "hey, we'll just compress 2048x1536 video on the computer, stream it over wifi, and decompress it on a tablet."