Use SPDX-License-Identifier: XXX in source files

Let's replace our current license disclaimer in files by an SPDX-License-Identifier.

Advantages

• More concise (less visual clutter at the beginning of the file)
• easy to parse by third-party tools
• easy to validate

See e.g. the Linux kernel that switched to SPDX-License-Identifier: https://lwn.net/Articles/739183/ . Also KDE has done so.

A template for setting up using SPDX-License-Identifier is available at https://reuse.software/spec/ . I'm not yet sure whether we can (and should) follow the framework 100% (there's e.g. a requirement to mark the license of every file, which is a bit annoying say for image files, and 3rd party code). But we should only deviate from the suggestions where necessary.

SPDX License Mapping

License files

Current license files (LICENSE.*) are removed from the main directory of each repository. Instead, licenses named after SPDX identifier:

• LICENSES/LicenseRef-Qt-Commercial.txt
• LICENSES/BSD-3-Clause.txt
• ...

Qt-Commercial would be a meta-license, like it is currently:

Licensees holding valid commercial Qt licenses may use this file in
accordance with the commercial license agreement provided with the
Software or, alternatively, in accordance with the terms contained in
a written agreement between you and The Qt Company. For licensing terms
and conditions see https://www.qt.io/terms-conditions. For further
information use the contact form at https://www.qt.io/contact-us.

Action Points

• Update qtqa license scanner so that it does not bark on missing QT_BEGIN_LICENSE: headers. Instead, consider adapting https://git.fsfe.org/reuse/tool .
• Mass-change all files, repository by repository (ignoring 3rd party code for now)