OpenZFS is a fork from before Oracle took ZFS closed again. It still has the CDDL license. OpenZFS is directly used by the people who maintain ZFS on various platforms (such as ZFS on Linux).
The end ZFS implementation can be used many places and ways. For instance, my employer believes that ZFS on Linux is safer and more reliable than btrfs is. Likewise, it is used on FreeBSD and various illumos (open source fork of Solaris) systems as the default file system.
While Oracle has presumably added new features to their ZFS, numerous companies have been working on OpenZFS for some time now and adding their own sets of new features that Oracle doesn't have, such as LZ4 compression.
The end ZFS implementation can be used many places and ways. For instance, my employer believes that ZFS on Linux is safer and more reliable than btrfs is. Likewise, it is used on FreeBSD and various illumos (open source fork of Solaris) systems as the default file system.
While Oracle has presumably added new features to their ZFS, numerous companies have been working on OpenZFS for some time now and adding their own sets of new features that Oracle doesn't have, such as LZ4 compression.