The argument really is based around what constitutes a derivative work. ZFS does not depend on Linux, OpenZFS which ZFS on Linux derives from is an Illumos proj

The argument really is based around what constitutes a derivative work. ZFS does not depend on Linux, OpenZFS which ZFS on Linux derives from is an Illumos project first and foremost - does modifying it to plug into the Linux VFS layer make it a derived work of the Linux kernel? If this ever goes to court it will be an interesting case.