Say I want to use the jQuery UI datepicker. I am not planning on using any other piece of jQuery UI.
I create a custom download with a custom theme. When creating my custom download, I only use the Datepicker lib, which only selects the Core lib as a dependency.
I download it and unzip it into my site dir and use it and it's great. But what if, in six months, another another developer needs to use another widget or tweak the theme or something. I know they could just edit it manually, but is there a way to get back to where you were at jqueryui.com, make your changes, and redownload?
If you open the original CSS file that was generated by Themeroller, you will find a comment that reads "To view and modify this theme, visit [some URL]". Just go to that URL and you'll be able to edit your theme.