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.