I'm always pretty wary of opinions given by non-lawyers (or even lawyers without subject matter experience) on specialized legal matters (With all due respect to Sheldon, he would not be qualified by a court to testify as an expert witness in copyright law). Here's a link to the skinny from the U.S. Copyright Office:
The "About Copyright" section, including a Frequently Asked Questions subsection, is pretty informative and written for laypersons.
IP (licensed in a couple of states and federal district courts) Merkin Providence, RI