Oracle started BTRFS as "me too" project to show SUN they can do something like ZFS (well, they couldn't). So after acquisition of SUN they ended up with both. SUN's strategy was to use ZFS as one of main selling points of Solaris and refused to port it to Linux; somebody someday decided to port it as well and ended up with ZFS with weird license and buggy BTRFS they slowly phased out to Red Hat and SuSE.