What does it mean that ZFS is included in Debian?
Petter Reinholdtsen recently blogged about ZFS availability in Debian. Many people have worked hard on getting ZFS support available in Debian and we would like to thank everyone involved in getting to this point and explain what ZFS in Debian means.
The landing of ZFS in the Debian archive was blocked for years due to licensing problems. Finally, the inclusion of ZFS was announced slightly more than a year ago, on April 2015 by the DPL at the time, Lucas Nussbaum who wrote "We received legal advice from Software Freedom Law Center about the inclusion of libdvdcss and ZFS in Debian, which should unblock the situation in both cases and enable us to ship them in Debian soon.". In January this year, the following DPL, Neil McGovern blogged with a lot of more details about the legal situation behind this and summarized it as "TLDR: It’s going in contrib, as a source only dkms module."
ZFS is not available exactly in Debian, since Debian is only what's included in the "main" section archive. What people really meant here is that ZFS code is now in included in "contrib" and it's available for users using DKMS.
Many people also mixed this with Ubuntu now including ZFS. However, Debian and Ubuntu are not doing the same, Ubuntu is shipping directly pre-built kernel modules, something that is considered to be a GPL violation. As the Software Freedom Conservancy wrote "while licensed under an acceptable license for Debian's Free Software Guidelines, also has a default use that can cause licensing problems for downstream Debian users".