Christian let me know that he doesn't have time right now to work on the
i18n issues that Siebrand identified in his modifications to the
SpecialUploadLocal extension. Meanwhile, Niklas says that these sort of
things should be easy for almost anyone to fix.
If you have an interest in i18n or SpecialUploadLocal, now is your chance
to get involved.
https://www.mediawiki.org/wiki/Special:Code/MediaWiki/104568
https://www.mediawiki.org/wiki/Extension:SpecialUploadLocal
Mark.