You know, Redox (as the "most serious" Rust kernel I can think of) could probably do with non-trivial drivers. It would be unfortunate for aspiring or even seasoned kernel developers to step away from the practice entirely, simply because R4L fails to launch.
Part of me feels like something like Redox isn't exactly worthit. Now I hope the project succeeds in whatever goals they have, and honestly where they've gotten to is impressive; what I mean to say is that I think it would be far more interesting to imagine beyond just Unix and especially the problems of POSIX. I think the "next" thing, if that even ever materializes needs to be that, something reimagined. Computers aren't emulated PDP-11's anymore.
