In my opinion, reimplementing ZFS from scratch would cost at least $100 million and take 5 to 10 years of development by many talented people. Given that we already have the source code under the CDDL and it is good enough, no one is willing to spend that kind of money. Why would they? There is no business case.
If anything, Oracle's software patents are a case against it because they could sue a clean room implementation like they did with Android's Java implementation. They would have a stronger case too due to the hundreds of patents covering ZFS. That is the elephant in the room with btrfs that no one discusses. :/
Anyway, I see no need to reimplement ZFS from scratch after consultation with attorneys of the SFLC and others.
Linux has a black-box reimplementation of DTrace (with different design sensibilities, but essentially all the same functionality) under the name of eBPF, and bcc for the userspace bits. Linux is trying to do that for ZFS under the name of btrfs, but it's not as good.
If anything, Oracle's software patents are a case against it because they could sue a clean room implementation like they did with Android's Java implementation. They would have a stronger case too due to the hundreds of patents covering ZFS. That is the elephant in the room with btrfs that no one discusses. :/
Anyway, I see no need to reimplement ZFS from scratch after consultation with attorneys of the SFLC and others.