ZFS is only 15 years old and continues to be improved (though granted, all of the real innovations have already happened). It works on (in order) Solaris, FreeBSD, Linux, MacOS, and Windows.
Maybe not (there's a reason I put macos and windows last), but the fact remains that people have put effort into making it portable, and it shows: ZFS runs well on more OSes than most other (non-toy) FSes.