Craig and others,

Best advice, consult an intellectual property attorney.

The US nows participates in the international copyright committee which does NOT require claiming the copyright at all.

It is possible in the US to register the copyright with the library of congress. When registered the copyright is NOT guaranteed, however in any action it is the responsibility of the other party to prove that you do not own the copyright. Without registration it is your responsibility to prove that you do own the copyright.

One simple, but possiblitiy not enforceable, way to protect your interest is to mail yourself a copy of the source code in a registered letter and do not open it. File it away. If an action ever ensues the letter can be opened in court, with the postmark, to prove when you wrote the code.