Well it seems I don't use 'distro' properly. I guess it only concerns Linux, but I personally don't see any reason it can't be used for OS flavors in general. Hell, the website distrowatch includes BSD and everything in between. Is there a similar phrase for BSD variants?

And ZFS is on a lot more than just FreeBSD, even if it's not official. ZFS started on OpenSolaris, not on FreeBSD. OS X has a port. Then FreeBSD got it's port. Linux has a stable port. And there are NAS OS's shipping with it like FreeNAS, TrueNAS, and a device called ReadyDATA by Netgear that has it.

I was mostly surprised at this: "The good stuff that probably won’t make it to NetBSD 7: Stable ZFS." So you're telling me ZFS isn't considered stable on NetBSD? It seems to be that it's pretty stable on quite a few other platforms, some mentioned above.