[tz] Single source of truth for timezone data

[Benjamin Drung]

On Sat, 2022-12-10 at 13:28 -0800, Paul Eggert wrote:
> On 2022-12-09 15:13, Benjamin Drung wrote:
> > 
> > https://github.com/unicode-org/cldr/blob/main/common/supplemental/metaZones.xml
> > says "Copyright © 1991-2013 Unicode, Inc." and "For terms of use, see
> > http://www.unicode.org/copyright.html".
> > This page points to https://www.unicode.org/license.txt
> 
> Thanks for pointing this out - I wasn't aware of the intent there. 
> Still, I see some legal issues. copyright.html defines Unicode data 
> files to be the data files published under the following URLs:
> 
>    https://www.unicode.org/Public/  (except PDF online code charts)
>    https://www.unicode.org/reports/
>    https://www.unicode.org/ivd/data/
> 
> license.txt says we have permission to redistribute modified versions of 
> these data files. However, I don't see anything that grants permission 
> to redistribute modified versions of
> <https://github.com/unicode-org/cldr/blob/main/common/supplemental/metaZones.xml> 
> (the file you mentioned) as I could not find it under any of the 
> abovementioned three URLs.
> 
> I expect the intent was that we have permission to redistribute working 
> data like that metaZones.xml URL even though it isn't part of an 
> official release, but if so the intent should be stated formally. (I've 
> learned to be cautious when it comes to copyright....)

https://github.com/unicode-org/cldr comes with unicode-license.txt. The
README.md says: "Usage of CLDR data and software is governed by the
Unicode Terms of Use a copy of which is included as unicode-
license.txt." and "SPDX-License-Identifier: Unicode-DFS-2016". Some of
the files in the repository have this SPDX license header. We should ask
them to add this license header to all relevant files including
metaZones.xml.

-- 
Benjamin Drung
Debian & Ubuntu Developer