A free Linux operating system that features the ZFS fileystem and illumos kernel
XStreamOS also offers a good starting point to develop and contribute to the illumos kernel. It is the base of other two full featured products created by Sonicle S.r.l., such as XStream Storage and XStream Server.
XStreamOS is distributed as separate ISO and USB images, supporting both 32-bit and 64-bit architectures. Free versions of XStream Server and XStream Storage will be available soon.