[tz] Single source of truth for timezone data

[Paul Eggert]

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....)