[X-Istence]

Apple had one point had read/write support for ZFS, but it was pulled because Sun at the time was not able to provide certain guarantees. There was an email by one of the main guys in ZFS that said something to that effect.

As such ZFS on Mac OS X is a dead project.

[wmf]

Some work is still being done outside of Apple: http://code.google.com/p/maczfs/ Maybe it's an undead project.

[deno]

I think PureDarwin folks are working on this. http://www.puredarwin.org/downloads/xmas