Back in the day it was assumed by writers that they needed to file their work with the Library of Congress to prove copyright.
Not so. But if you want to prove your authorship of open source code and protect it from patent trolls, perhaps you should file. With Linux Defenders.
Linux Defenders is the creation of the Open Innovation Network, a group that includes Red Hat, IBM, Novell and others interested in protecting open source rights.
http://www.linuxlinks.com/portal/news/article.php?story=20081210132553174