[tz] Use or Apply for SPDX Licence

[Paul.Koning at dell.com]

> On Jun 20, 2020, at 4:43 PM, Kim Davies <kim.davies at iana.org> wrote:
> 
> 
> [EXTERNAL EMAIL] 
> 
> Quoting Brian Inglis on Saturday June 20, 2020:
>> 
>> It would be useful to distributions, packagers, and organization licence
>> checkers if the tzcode and tzdata were covered by (a) Public Domain SPDX licence
>> identifier(s) WTFPL, etc. or applied for it's own e.g. IANA-TZ-PD.
> 
> In response to a few different requests that the IANA registries have
> more explicit licensing, we've been working with the IETF and IETF Trust
> recently on developing an approach to licensing that preserves the current
> nature but makes it clear. We'll take this tagging into consideration.
> 
> kim

I don't get it.  Much of the material is marked "public domain".  That has a precise meaning.  Licenses are different from public domain.  Why is anything needed here?

	paul