nilfs2: clarify permission to replicate the design

To respond to a certain developer's request, this explicitly state that
developers can reimplement the nilfs2 design for other operating systems
to share data stored in that format.

Link: http://lkml.kernel.org/r/1461935747-10380-7-git-send-email-konishi.ryusuke@lab.ntt.co.jp
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/filesystems/nilfs2.txt

@@ -268,3 +268,8 @@ among NILFS2 files can be depicted as follows:
                                     ( regular file, directory, or symlink )
 
 For detail on the format of each file, please see include/linux/nilfs2_fs.h.
+
+There are no patents or other intellectual property that we protect
+with regard to the design of NILFS2.  It is allowed to replicate the
+design in hopes that other operating systems could share (mount, read,
+write, etc.) data stored in this format.