Bug#696185: [copyright-format] Use short names from SPDX

[Simon McVittie <smcv@debian.org>]

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On Sat, 03 Sep 2022 at 16:22:46 +0500, Akbarkhon Variskhanov wrote:
> FSF[1] as well as SPDX[2] request using the suffixes "-only" or
> "-or-later" with GNU licenses:
> 
> > Therefore, when you use SPDX license indicators, please use these:
> > GPL-2.0-only or GPL-2.0-or-later
> 
> DEP-5 uses the bare form, i.e. "GPL-3" or "GPL-3+". I added this
> difference to the wiki page.
> 
> What's not clear is how are we going to approach this discrepancy?
> Shall we a) ignore this, b) adopt SPDX/FSF naming, or c) suggest SPDX
> to stick to uniform naming convention, which is using "+" to denote
> later versions of a license?

Sorry, (c) seems very unlikely: earlier versions of SPDX had the same
convention as DEP-5, but later versions moved to "GPL-2.0-only" and
"GPL-2.0-or-later", which I think was the result of a request from the
FSF to make it clearer whether the "or later" clause of the {A,L,}GPL
family was allowed or excluded.

Forms like GPL-2.0, LGPL-3.0+ and so on are still listed in
https://spdx.org/licenses/ as deprecated equivalents of GPL-2.0-only,
LGPL-3.0-or-later and so on.

I would personally be in favour of (b) as our long-term direction,
but for now the status quo is basically a variation of (a): keep using
the Debian-specific names where they exist, but where there is no
Debian-specific name for a license, the SPDX name is as good a name as
any other.

> [2] https://spdx.dev/ids/

I believe the canonical reference for the SPDX license identifiers is
https://spdx.org/licenses/ which also lists all the deprecated forms.

    smcv