This is a really interesting project! It would be interesting to adapt it to old laptops. They are a dime a dozen and if people could donate them then they could serve this same purpose.
It's just software running on a Raspberry Pi (which does have TV out). You could easily run the exact same software on a laptop. Maybe even build a FreeDOS version, for maximum availability on x86 retro hardware. (Though this is actually an obvious use case for a DRM-free ebook platform. If only e-paper in large formats wasn't so expensive and hard to find.)
Part of the problem with repurposing old laptops is they're vulnerable to battery failure, at which point they're just awkward all-in-one PCs chained to a power adapter. None of my old laptops are in usable condition without a battery swap, and I suspect the cost of a raspberry pi isn't much higher than a new battery...
> I suspect the cost of a raspberry pi isn't much higher than a new battery.
Don't forget that you'd have to factor in the cost of a display, input devices, and storage if you go the Raspberry Pi route. And if you wanted the Pi to be portable (as your alternative suggestion seemingly implies) you'd have to buy a battery for it as well.
On the other hand, if you don't need the Pi to be portable, you might as well just leave the laptop plugged in and use it instead, as you wouldn't have to spend any money at all to achieve the same end-result as purchasing the Pi.
In fact, I would wager that putting together a Raspberry Pi solution comparable to a cheap laptop would be difficult for any given price point; if the laptop is just "old" and not "broken", I would further argue that it provides a much better user-experience.
I don't intend for this to be a criticism of the Raspberry Pi. In the article they're using old CRT televisions which negate the cost of a display, and keyboards and mice are readily available from a number of places for free (or close to it). For their use-case, it seems to be quite an effective solution.