Oracle sells Oracle Linux, a RedHat clone. ZFS on Linux (ZoL) isn't controlled by Oracle, it is a fork of OpenSolaris version of ZFS. The ZFS sold by Oracle on Solaris isn't the same product and doesn't support Linux. Oracle doesn't want to support it on Linux because it would fragment one of the remaining cash cow they got from Sun. And anyway, they probably can't support ZoL even if they wanted to without putting themselves into self induced legal gray water. Apparently, they intend to move Solaris into a rolling model like Windows 10, but focused on legacy. They can sell ZFS there without affecting their Linux operations. There is also a rumor of a deal with NetApp not to support ZFS on Linux. All combined, BTRFS is a better suited tech for them to support.
illumos is the repo of record for OpenZFS[1], which is the community fork of OpenSolaris' ZFS (which is now proprietary). Most of the really cool new features are in OpenZFS because it has far more developer involvement (from FreeBSD, illumos, etc).
Basically ZFS is Solaris (Oracle), everything else is OpenZFS. And every Solaris-like OS is at best just going to be an OpenSolaris (or derivative) fork.
No, they split when Oracle bought Sun. The only part of OpenZFS, which everything but Solaris uses, that involves Oracle is a number of patents that the CDDL grants permission to use.
This is a bit of a tangent, but I think it's important to remember that a huge corporation like Oracle has quite a different decision making process than individuals.
Yes, one devision of Oracle owns, maintains and develops ZFS. But one of the many other divisions (maybe for historical reasons, maybe because it was acquired and never migrated, ...) might use btrfs, and it makes sense for them to pour manpower into it, even if that could be perceived as somewhat of a competition to ZFS.
My main point is that big organizations naturally tend to do things that look conflicting from the outside, just because they are too large to be efficiently standardized.
> This is a bit of a tangent, but I think it's important to remember that a huge corporation like Oracle has quite a different decision making process than individuals.
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.
They started btrfs several years before they acquired Sun and ZFS with it. Why they continued with it is unclear, presumably a combination of inertia and not wanting to relicense it for other Linux's to be able to ship with.
