Allows post authors to easily add and manage footnotes in posts.
That's totally simple. Go and check out the manual.
Sure can! Feature requests (and bug reports) are best made via the WordPress Plugins bug tracker.
If you fancy being even more helpful, you can write some code and submit a pull request.
Because answers to pretty much all the questions that get asked frequently are in the manual.
This plugin is licensed under the same license as WordPress itself, the GPLv2 (or later).