The license preview in Special:Upload doesn't respect ?uselang=... override.
It'll fire an API request to parse the selected license without passing along the current language (causing it to parse in the user's preferred/default language)
We should probably specify the current user language to the API call to make sure it matches the rest of the interface:
i.e. add
uselang: mw.config.get('wgUserLanguage')
to https://github.com/wikimedia/mediawiki/blob/master/resources/src/mediawiki.special/mediawiki.special.upload.js#L132