In other words they stuck some Illumos based distribution like OpenIndiana or SmartOS on top of commodity hardware, added a Web UI, and called it a day. ZFS deduplication is a notorious memory hog and not recommended for production use. Compression works very well, on the other hand.
As for BTRFS, it is at least 5 years behind in terms of maturity and robustness, ZFS is available for Linux as well, just not shipping together because it's license is not ideologically pure enough for the ayatollahs of GPL.