LICENSES: Rename other to deprecated

Make it clear in the directory name that these are not intended for new
code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

LICENSES: Clearly mark dual license only licenses

Just like the CDDL the Apache license and the MPL must only be used as
a choice in additional to an GPL2 compatible license. Copy over the
boilerplate from the CDDL file to the other two after fixing it up to
make it clear the licenses need to be GPL2 compatible, not just the
more generic GPL compatible. For example the Apache 2 license is GPL3
compatible, but that doesn't matter for the kernel.

Also move these licenses to a separate directory and document the rules
in license-rules.rst.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: Don't reference the ZLib license in license-rules.rst

We never had a file called LICENSES/other/ZLib in the tree, so don't
reference it. Instead mention the GPL v1 as an (bad) example.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

doc: fix typos in license-rules.rst

The patches fixes some typos in process/license-rules.rst

Signed-off-by: Federico Vaga <federico.vaga@vaga.pv.it>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

module: Cure the MODULE_LICENSE "GPL" vs. "GPL v2" bogosity

The original MODULE_LICENSE string for kernel modules licensed under the
GPL v2 (only / or later) was simply "GPL", which was - and still is -
completely sufficient for the purpose of module loading and checking
whether the module is free software or proprietary.

In January 2003 this was changed with commit 3344ea3ad4b7 ("[PATCH]
MODULE_LICENSE and EXPORT_SYMBOL_GPL support"). This commit can be found in
the history git repository which holds the 1:1 import of Linus' bitkeeper
repository:

https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=3344ea3ad4b7c302c846a680dbaeedf96ed45c02

The main intention of the patch was to refuse linking proprietary modules
against symbols exported with EXPORT_SYMBOL_GPL() at module load time.

As a completely undocumented side effect it also introduced the distinction
between "GPL" and "GPL v2" MODULE_LICENSE() strings:

* "GPL" [GNU Public License v2 or later]
* "GPL v2" [GNU Public License v2]
* "GPL and additional rights" [GNU Public License v2 rights and more]
* "Dual BSD/GPL" [GNU Public License v2
* or BSD license choice]
* "Dual MPL/GPL" [GNU Public License v2
* or Mozilla license choice]

This distinction was and still is wrong in several aspects:

1) It broke all modules which were using the "GPL" string in the
MODULE_LICENSE() already and were licensed under GPL v2 only.

A quick license scan over the tree at that time shows that at least 480
out of 1484 modules have been affected by this change back then. The
number is probably way higher as this was just a quick check for
clearly identifiable license information.

There was exactly ONE instance of a "GPL v2" module license string in
the kernel back then - drivers/net/tulip/xircom_tulip_cb.c which
otherwise had no license information at all. There is no indication
that the change above is any way related to this driver. The change
happend with the 2.4.11 release which was on Oct. 9 2001 - so quite
some time before the above commit. Unfortunately there is no trace on
the intertubes to any discussion of this.

2) The dual licensed strings became ill defined as well because following
the "GPL" vs. "GPL v2" distinction all dual licensed (or additional
rights) MODULE_LICENSE strings would either require those dual licensed
modules to be licensed under GPL v2 or later or just be unspecified for
the dual licensing case. Neither choice is coherent with the GPL
distinction.

Due to the lack of a proper changelog and no real discussion on the patch
submission other than a few implementation details, it's completely unclear
why this distinction was introduced at all. Other than the comment in the
module header file exists no documentation for this at all.

From a license compliance and license scanning POV this distinction is a
total nightmare.

As of 5.0-rc2 2873 out of 9200 instances of MODULE_LICENSE() strings are
conflicting with the actual license in the source code (either SPDX or
license boilerplate/reference). A comparison between the scan of the
history tree and a scan of current Linus tree shows to the extent that the
git rename detection over Linus tree grafted with the history tree is
halfways complete that almost none of the files which got broken in 2003
have been cleaned up vs. the MODULE_LICENSE string. So subtracting those
480 known instances from the conflicting 2800 of today more than 25% of the
module authors got it wrong and it's a high propability that a large
portion of the rest just got it right by chance.

There is no value for the module loader to convey the detailed license
information as the only decision to be made is whether the module is free
software or not.

The "and additional rights", "BSD" and "MPL" strings are not conclusive
license information either. So there is no point in trying to make the GPL
part conclusive and exact. As shown above it's already non conclusive for
dual licensing and incoherent with a large portion of the module source.

As an unintended side effect this distinction causes a major headache for
license compliance, license scanners and the ongoing effort to clean up the
license mess of the kernel.

Therefore remove the well meant, but ill defined, distinction between "GPL"
and "GPL v2" and document that:

- "GPL" and "GPL v2" both express that the module is licensed under GPLv2
(without a distinction of 'only' and 'or later') and is therefore kernel
license compliant.

- None of the MODULE_LICENSE strings can be used for expressing or
determining the exact license

- Their sole purpose is to decide whether the module is free software or
not.

Add a MODULE_LICENSE subsection to the license rule documentation as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Philippe Ombredanne <pombredanne@nexb.com>
Acked-by: Joe Perches <joe@perches.com>
[jc: Did s/merily/merely/ ]
Acked-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

docs: tidy up TOCs and refs to license-rules.rst

The documentation and TOCs are organized in a manner of a tree. Adding a TOC to
the root, which refers to a file which is located in a subfolder forms a
grid. Those TOCs are a bit confusing and thats why we get additional error
messages while building partial documentation::

$ make SPHINXDIRS=process htmldocs
...
checking consistency... Documentation/process/license-rules.rst: \
WARNING: document isn't included in any toctree

To fix it, the *root-license-TOC* is replaced by a reference and the
'license-roles.txt' is added to the Documentation/process/index.rst TOC.

BTW: there was an old licences remark in Documentation/process/howto.rst which
is also updated, mentioning SPDX and pointing to the license-rules.rst

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

COPYING: create a new file with points to the Kernel license files

With the addition of SPDX patchset, the contents of COPYING file
is now duplicated at two other files under LICENSE:
LICENSES/preferred/GPL-2.0
LICENSES/exceptions/Linux-syscall-note

It is easy to check that the contents of the licence written on
those files are identical with COPYING using:

$ diff -upr COPYING LICENSES/preferred/GPL-2.0
$ diff -upr COPYING LICENSES/exceptions/Linux-syscall-note|less

Also, a new file was added, with describes how SPDX should work at
the Kernel source files:
Documentation/process/license-rules.rst

Instead fo having it copying the contents of two files, and not
even mentioning the third one, replace it by a file whose content
points to the other tree files, preserving the Kernel's license.

Adjust license-rules.rst accordingly.

Please notice that this file preserves the Kernel license as
is, without any changes.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation: Add license-rules.rst to describe how to properly identify file licenses

Add a file to the Documentation directory to describe how file licenses
should be described in all kernel files, using the SPDX identifier, as well
as where all licenses should be in the kernel source tree for people to
refer to (LICENSES/).

Thanks to Kate and Greg for review and editing and Jonas for the
suggestions concerning the meta tags in the licenses files.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jonas Oberg <jonas@fsfe.org>
Reviewed-by: Jonathan Corbet <corbet@lwn.net>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>