Hrm, yes-we-scan and printervention are built on SANE and CUPS respectively, which makes sense. But running them in a whole wasm-emulated Linux kernel and userland seems... like a lot.
If you just need a single scan every now and then and have an old scanner, I can see this being handy. Installing Linux, battling Windows drivers or buying Vuescan (great as it is) might be enough to make most just give up and take a photo of whatever document they where going to scan.
It is a little much, but if it can be made to "Just Work" by booting a Linux kernel in the browser that it pretty cool and impressive. I'm still a little on the fence about my browser having USB support, but this could be handy for dusins of people.
Ah, it seems like the architecture was designed by a slop machine. OK.
Oh, and:
> I must apologise that I haven’t so far open-sourced any part of this that I don’t have to.
With some blather about commercial opportunities. Which is a weird thing to say without linking to the bits that must be shared (under the terms of the various licenses).