The MultiUpload extension has been unmaintained for a while. I believe its author has moved on to another job. I've written a completely independent piece of extension code (as a byproduct of work I did for the WorkingWiki extension) that provides a multiple-upload interface. After consulting with Petrb, who is listed as the current maintainer of MultiUpload on mediawiki.org, I'm thinking of checking in my multiple-upload code as a new version of MultiUpload, completely replacing the current implementation.
I'm posting here in case anyone objects or cares to raise concerns.
Here's a bare-bones demo video: https://www.youtube.com/watch?v=4d90Tt5EGAc
And here's my extension, in a temporary location: https://github.com/worden-lee/MultiUpload
Lee Worden