Apple was already working to integrate ZFS when Oracle bought Sun.
From TFA:
> ZFS was featured in the keynotes, it was on the developer disc handed out to attendees, and it was even mentioned on the Mac OS X Server website. Apple had been working on its port since 2006 and now it was functional enough to be put on full display.
However, once Oracle bought Sun, the deal was off.
Again from TFA:
> The Apple-ZFS deal was brought for Larry Ellison's approval, the first-born child of the conquered land brought to be blessed by the new king. "I'll tell you about doing business with my best friend Steve Jobs," he apparently said, "I don't do business with my best friend Steve Jobs."
And that was the end.