What the... This isn't any kind of new idea. He's built a very slow teletype without a proper modem in it. CLIs and text adventures work the way they do because they were originally developed on teletype mainframe terminals...
And if that isn't an electric typewriter (...70s, I'd say, a cheap Smith-Corona alternative to the ubiquitous 60s daisywheel/golfball IBM Selectrics) I'll be surprised, given the short-travel super-light-touch keys, very consistent character weight (& film inking rather than ribbon), push button CR/LF and a few suspicious-looking switch-esque things on the case. I have no freakin' idea what all those enormous solenoids at the back are doing (can't see any connection to the typewriter itself) but they're maybe for effect, or doing the job of relays. Perhaps the internals of the original beast are running at AC line voltage and it was the only way to easily and safely wire it up to the USB link.
(If it IS a manual, I'd quite like one, as having something entirely mechanical and unpowered to bang out documents on that wouldn't lead to massive finger cramp would be a handy thing to have around)
I don't wish to belittle the work put in, as it's obviously been extensive (and is far, far more awesome than anything I've made or could wish to), and it would otherwise be a cool idea... but, teletype terminal + USB-Serial converter of the right type = superior
(Well ... OK ... maybe not. This has the advantage that it can do lowercase and a full range of punctuation)
Now, if he can take the same idea and apply it to an old 1920s Remington or something, including having to backspace and overprint to create exclamation marks etc, then we'll be talking proper steampunkage. Just in time to be one-upped by someone who converts the screen output to an audio morse signal and feeds it into a 19th century railroad telegraph or stock ticker.