P. Chandra

Adds copyright notice at end of articles in full text RSS feeds, with back links to the blog and original article.
A notice gets attached at the bottom of feed articles like this 
Original Article: Title of Article (linked to permalink) 
Copyright Year. Blog Title (linked). All Rights Reserved
Your Blog title is linked to your blog Url. Your article title is linked to the article permalink.
Blog copyright notices are important as your feed gets freely distributed across the web and is republished without permission by RSS scrappers and autoblogs. After using this plugin, now RSS scrappers will link back to your site, which will suggest to search engines that your blog and article was the original source.

Simple Feed Copyright

Adds copyright notice at end of articles in full text RSS feeds, with back links to the blog and original article.

adamh

Feed Extensions allows you to add any text or html to the bottom of the footer. Tags such as [blog_name], [blog_url] or [year] can be inserted.
This is my first plugin on WordPress/Extend – I’d be grateful of any suggestions on how to improve the plugin. Thanks!

Feed Extensions

Feed Extensions allows you to put footer text at the bottom of each post in your feed.

Simple Feed Copyright vs Feed Extensions