= COPYING.adoc for the Khronos Group OpenXR projects

// Copyright (c) 2020-2021, The Khronos Group Inc.
//
// SPDX-License-Identifier: CC-BY-4.0

This document is shared across a number of OpenXR GitHub projects, as the
set of files in those projects is partially overlapping.
(There is a single "source of truth" internal Khronos GitLab repo these
GitHub repositories interact with.)

== Licenses

The OpenXR GitHub projects use several licenses.
In general, we work to maintain compliance with the
https://reuse.software/spec/[REUSE 3.0 specification] with clear copyright
holders and license identifier listed for each file, preferably in each
file.
Where this is not possible, or e.g. when we are using files unmodified from
other open-source projects, license data is listed:

* in an adjacent file of the same name, with the additional extension
  "`.license`"
* in the repository-wide "`.reuse/dep5`" copyright description
  https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/["DEP5"
  machine-readable copyright data] file.

The https://github.com/fsfe/reuse-tool["`reuse`" command line tool] can be
used to create a software bill of materials in SPDX format from this data.
Note that this tool will typically exclude the generated files, so if the
BOM is important to you, you may consider using the
https://github.com/KhronosGroup/OpenXR-SDK[OpenXR-SDK] repository that
contains the API headers and the loader source with all generated files
pre-generated.

The data in/adjacent to each file is the authoritative license and copyright
data.
However, for ease of understanding, the following general practices can be
observed.
(If in doubt, or if the following summary conflicts with the per-file data,
the per-file data remains authoritative.)

* The source files (in asciidoctor and other formats) for the OpenXR
  Specification, reference pages, and supporting documentation are licensed
  under the Creative Commons Attribution 4.0 International License (SPDX
  license identifier "`CC-BY-4.0`").
* Header files, scripts, programs, XML files, and other tooling used or
  generated as part of the build process is licensed under the Apache
  License, Version 2.0.
* For compatibility with external developers working in GPLed projects who
  have requested it, the main OpenXR headers, XML registry, and loader
  source are licensed under a dual license with the SPDX license identifier
  "`Apache-2.0 OR MIT`" .
  Relevant files include:
** "`specification/registry/xr.xml`"
** "`include/openxr/openxr_platform_defines.h`"
** The generated OpenXR headers "`openxr.h`", "`openxr_platform.h`", and
   "`openxr_reflection.h`".
** Source files in "`src/loader/`", and a few files in "`src/common/`".
** Generated source files used by the loader (including pre-generated in
   OpenXR-SDK): "`common_config.h`", "`xr_generated_loader.cpp`", and
   "`xr_generated_loader.hpp`".
* There are a few files adopted from other open source projects.
  Such files continue under their original licenses, and appropriately
  annotated in accordance with REUSE.
* Some generated, transient files produced during the course of building the
  specification, headers, or other targets may not have copyrights.
  These are typically very short asciidoc fragments describing parts of the
  OpenXR API, and are incorporated by reference into specification or
  reference page builds.

Users outside Khronos who create and post OpenXR Specifications, whether
modified or not, should use the CC-BY-4.0 license on the output documents
(HTML, PDF, etc.) they generate.


== Frequently Asked Questions

Q: Why are the HTML and PDF Specifications posted on Khronos' website under
a license which is neither CC-BY-4.0 nor Apache 2.0?

A: The Specifications posted by Khronos in the OpenXR Registry are licensed
under the proprietary Khronos Specification License.
Only these Specifications are Ratified by the Khronos Board of Promoters,
and therefore they are the only Specifications covered by the Khronos
Intellectual Property Rights Policy.


Q: Does Khronos allow the creation and distribution of modified versions of
the OpenXR Specification, such as translations to other languages?

A: Yes.
Such modified Specifications, since they are not created by Khronos, should
be placed under the CC-BY-4.0 license.
If you believe your modifications are of general interest, consider
contributing them back by making a pull request (PR) on the OpenXR-Docs
project.


Q: Can I contribute changes to the OpenXR Specification?

A: Yes, by opening an Issue or Pull Request (PR) on the
link:https://github.com/KhronosGroup/OpenXR-Docs/[OpenXR-Docs] GitHub
project.
You must execute a click-through Contributor License Agreement, which brings
your changes under the umbrella of the Khronos IP policy.


Q: Can you change the license on your files so they're compatible with my
license?

A: We are using a dual license license on `xr.xml`, the main API headers,
and the loader source files, to make them compatible with GPL-2.0- and
LGPL-2.0/2.1-licensed projects.
This replaces earlier approaches of an MIT-like license on the XML and
Apache 2.0 on all headers, and allows use of the SPDX license identifier
"`Apache-2.0 OR MIT`" to denote the license.

If you *require* this same compatibility for use of other Apache-2.0
licensed files in our repository, please raise an issue identifying the
files and we will consider changing those specific files to the dual license
as well.

