Distributions

The following open-source operating system distributions use Open ZFS (listed alphabetically):

illumos-based

OmniOS

• general-purpose server OS
• download page; source code
• commercial support available from OmniTI

OpenIndiana

• general-purpose server OS
• download page; source code

FreeBSD-based

FreeBSD

• general-purpose server OS
• download page; source code

FreeNAS

• NAS appliance software, based on FreeBSD
• commercial support available for sister product TrueNAS from ixSystems

incomplete list, please help!

Debian GNU/kFreeBSD

• Debian variant with ~90% of the same software packages, based on GNU libc, but using the FreeBSD kernel which provides ZFS
• Installer supports creation of ZFS pools, installing to them, and booting directly from them with GRUB2
• We'd like to know how we're doing, and what major features are missing (DTrace comes to mind)

Linux-based

ZFS on Linux

• ZFS on Linux provides self-building packages for Debian, Fedora, RHEL/CentOS/SL, Ubuntu and build instructions for several other distributions

Gentoo

• Gentoo provides first-party ZFSOnLinux packages to itself and its derivatives.