It is just tedious and you need motivation. Especially as Linux has a lot of interfaces, many of which are frustratingly annoying - there are three file change notification interfaces, of different dates. In fact there are at least two of everything!

I amagine much of the Joyent code could be easily ported to NetBSD/FreeBSD (which now has a 64 bit interface as of a few months back). epoll may well be the most difficult (it has edge and level triggered events and other annoyances). But a not very performant version should be doable.

Mostly, few people have been interested. I have a decent test suite though (rump based) so email if you are interested...