Licensing guidelines for AppStream project_license

[Otto Urpelainen]

Hello packagers,

During the package review of qvge [1], the following question came up: 
Are the any requirements placed on the contents of AppStream metadata, 
particularly the field project_license [2]? It feels natural that is 
MUST be the same (module differences in notation) as specfile License, 
since both have the same meaning. However, I cannot find anything in 
Licensing Guidelines about this.

In my experience, this comes up quite often, since upstreams often have 
bundled dependencies or other copy-pasted code with different license 
than upstream's own code, yet AppStream metadata, LICENSE file, README 
and so only list upstream's own license.

[1]: https://bugzilla.redhat.com/show_bug.cgi?id=1913870
[2]: 
https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#tag-p...

Otto