Add a section on license names to the MacPorts guide?

[Joshua Root]

See also <https://trac.macports.org/wiki/PortfileRecipes#license> and
<https://trac.macports.org/wiki/PortfileRecipes#licensekeyword>.

I wouldn't say this is the list of valid licenses, but rather the list
of ones our script knows about. Other licenses are fine but will need to
be added if it says "not known to be distributable".

We mostly use the identifiers from <https://spdx.org/licenses/> but with
a few differences, like all the BSD variants without an advertising
clause are pretty much equivalent for our purposes, and the versioning
info that is already in the guide.

In practice, for the purposes of determining distributability, licenses
really only fall into a few categories:
1. Licenses that completely prohibit redistribution of either binaries
and source, or binaries only
2. GPL or GPL-like ("no additional restrictions" language)
3. Licenses that conflict with some of the licenses in 2.
4. Licenses that don't conflict with any others

This is why a lot of the time, instead of adding a new license to the
checking script, we'll just use a generic term like "Permissive" or
"Restrictive/Distributable".

It's been suggested that we support all the SPDX identifiers. If we do
that, we could probably just map them to the above categories internally.

- Josh

On 2018-4-24 05:19 , Perry E. Metzger wrote:
> I'm thinking of adding the following to the MacPorts guide because we
> often have problems with people picking invalid license names in
> Portfile submissions.
> 
> That said, I'm not sure this is the best text for it. Thoughts?
> 
> Perry
> 
> diff --git a/guide/xml/portfile-keywords.xml b/guide/xml/portfile-keywords.xml
> index 77559a4..066cc53 100644
> --- a/guide/xml/portfile-keywords.xml
> +++ b/guide/xml/portfile-keywords.xml
> @@ -244,6 +244,16 @@
>          sub-list.
>          </para>
>  
> +        <para>Valid licenses are one of the following: afl agpl apache
> +        apsl artistic autoconf beopen bitstreamvera boost bsd bsd-old
> +        cc-by cc-by-sa cddl cecill cecill-b cecill-c cnri copyleft cpl
> +        curl epl fpll fontconfig freetype gd gfdl gpl gplconflict
> +        ibmpl ijg isc jasper lgpl libtool lppl mit mpl ncsa
> +        noncommercial openldap openssl permissive php psf
> +        public-domain qpl restrictive/distributable ruby sleepycat
> +        ssleay tcl/tk vim w3c wtfpl wxwidgets x11 zlib zpl
> +        </para>
> +
>          <para>If the version number is a
>          <quote>.0</quote> version, the <quote>.0</quote> should be
>          omitted to make the version an integer. If the author gives the choice
> 
>