Copyright Laws In Summary  

• These days, almost all things are copyrighted the moment they are written, and no copyright notice is required.
• Copyright is still violated whether you charged money or not, only damages are affected by that.
• Postings to the net are not granted to the public domain, and don't grant you any permission to do further copying except perhaps the sort of copying the poster might have expected in the ordinary flow of the net.
• Fair use is a complex doctrine meant to allow certain valuable social purposes.
• Copyright is not lost because you don't defend it; that's a concept from trademark law.
• Fan fiction and other work derived from copyrighted works is a copyright violation.
• Posting E-mail is technically a violation, but revealing facts from E-mail you got isn't, and for almost all typical E-mail, nobody could wring any damages from you for posting it. The law doesn't do much to protect works with no commercial value.
• Pictures and sounds have copyrights too, but domain names don't (that's a trade mark).