Intended for development environments, allows permissions to be granted so some users can modify CSS, either sitewide or only for themselves.
This came about because of a real scenario in my last project. I did not have direct access to the server filesystem, but was developing content I wanted to style consistently with CSS rather than inline. I was tweaking CSS in the browser using Firebug-like tools, building up a local CSS file, and occasionally sending them to the site administrator to copy to the site's filesystem. This wasn't an ideal workflow :(
I thought that with a tool like this, I could have been granted permission to edit global CSS on the development server, updated it as I worked, the client (site owner) could have seen my work as I intended, and the site admin (developer) could have been left in peace. At the end of content development, before deployment to the production environment, my CSS could have been integrated into the site/theme CSS properly.
Ah well, maybe next time. I hope this is useful to someone else for the same reasons or we can find other use cases.
Happily, CSS settings made in this module seem to take immediate effect without any cache flushing.