I'll throw in my 2 cents worth. I don't have any experience with publishing, but I did spend the last 10 years of my career as the intellectual property manager of a major oil company. I worked mostly with patents and trade secrets, but our outside council was a major intellectual property group. My impression fromtalking with them is that copyrights in the US are now implied, whether registered or not. Using anything without explicit permission in a work for profit could potentially cause a lot of headache.
