SPDX license identifier

[hudokkow]

Description

Clean up the mess with copyright notices and replace with an SPDX license identifier. It allows better overview of licenses, for both humans and compliance software. Done following the example of the Linux Kernel folks.

Motivation and Context

Modernization. Replaces #13927

How Has This Been Done/Tested?

1. Run scancode on master branch ./scancode -l -n 16 ../kodi --html ../kodi_licenses.html.
2. Identify all licenses spewed by it.
3. Group files with same license.
4. Confirm group by group, file by file if detected license is correct. Many are false positives because an expression or phrase triggers them. That's the case for all detected gpl-1.0-plus, triggered by http://www.gnu.org/copyleft/gpl.html.
5. If license is not clear (missing text, ambiguous interpretation, etc.) try to confirm with original author/sources. That was the case with xbmc/platform/win32/dxerr.h and xbmc/platform/win32/dxerr.cpp that looked like MS-PL licensed files but were indeed MIT licensed.
6. After initial assessment, pick a license group and change notice.
7. Loop.
8. Finally, take care of the biggest group, in our case GPL-2.0-or-later. Patterns are easy to find and sed is a very good friend.
9. Select a random sample of files and have a look to see if everything is OK.

Current licenses under xbmc/ (as seen on SPDX licenses list):

License	FSF Free/Libre	OSI Approved	GPLv2 Compat
BSD-3-Clause	✔️	✔️	✔️
BSD-4-Clause	✔️	❌	❌
GPL-2.0-only	✔️	✔️	✔️
GPL-2.0-or-later	✔️	✔️	✔️
LGPL-2.1-or-later	✔️	✔️	✔️
MIT	✔️	✔️	✔️
Unlicense (Public Domain)	✔️	❓	✔️

Last two commits uniformize our copyright line. Instead of a gazillion variations, we now have:

 *  Copyright (C) 2002-2018 Team Kodi
 *  Copyright (C) 2003-2018 Team Kodi
 *  Copyright (C) 2005-2018 Team Kodi
 *  Copyright (C) 2006-2018 Team Kodi
 *  Copyright (C) 2007-2018 Team Kodi
 *  Copyright (C) 2008-2018 Team Kodi
 *  Copyright (C) 2009-2018 Team Kodi
 *  Copyright (C) 2010-2018 Team Kodi
 *  Copyright (C) 2011-2018 Team Kodi
 *  Copyright (C) 2012-2018 Team Kodi
 *  Copyright (C) 2013-2018 Team Kodi
 *  Copyright (C) 2014-2018 Team Kodi
 *  Copyright (C) 2015-2018 Team Kodi
 *  Copyright (C) 2016-2018 Team Kodi
 *  Copyright (C) 2017-2018 Team Kodi
 *  Copyright (C) 2018 Team Kodi

Third-party copyright lines were not touched.

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

[natethomas]

Nice work. I can't imagine how long this took to do.

[CvH]

@hudokkow how do you "label" your *.jpg, *.png ... (media) files ? Currently (If I got this right) they are not covered by any licence at all. Shouldn't they have some Media Licence (like CC ...) and should be declared ?

[hudokkow]

@CvH, I haven't gotten around to those yet. This PR only deals with xbmc/ dir (roughly 43% of the almost 8500 files we're tracking).

As for your question, REUSE Initiative states:

All source files which are included in the final build of your project (verbatim, modified, partially, or in compiled form) must have copyright and license information contained within them. If it is not possible to add a header to the file, either because the file is a binary or because the format does not support comments, you must provide the information separately in one of three ways:

You may include a textfile called FILENAME.license in which you store your regular comment header with all the necessary information to convey the license information about the file called FILENAME.

If you have many such files, but each have the same copyright notice and license, you may instead use the DEP-5/copyright file format, and place a single copyright notice documenting those files.

If you have a way of automatically generating an inventory of included files in SPDX format (see practice 3), you may use this and do not need to separately include a .license file or DEP-5/copyright file.

reuse tool has a lint mode that does wonders to tell you what files are missing a copyright/license notice. Unfortunately I only found it after manually digging for all the files missing license and/or copyright notice. 😞

[garbear]

This PR is awesome. The commits are a good breakdown of our code's licenses. Thanks!