I am quoting Nikerabbit as he observed this:
"When the 'license-name' key is specified, this file is interpreted as wikitext."
One solution is to convert the existing COPYING files into wikitext another one will probably be to both allow text as well as wikitext.
Whatever is done should probably be done for MW 1.23 LTS too.
Examples:
[1] https://www.mediawiki.org/wiki/Special:Version/License/CentralNotice
[2] http://dev.translatewiki.net/wiki/Special:Version/License/Semantic_Forms
Version: 1.23.0
Severity: major