It builds on FreeBSD (soon OS X), but it's not working yet.

Replacing the epoll() with kevent() looks pretty straightforward if you want to try it out, but FreeBSD should be able to do other tricks as well (e.g. http filters)

Which is why most "competitors" go for libevent (or libuv), as that abstracts over all the various select(3) improvements.

Turbo does not just support Lua, it's actually written with it.