@rdr@ridge CC0 is a better license than the one in OP or public domain, because many places actually do not have proper methods or make it difficult to submit to the public domain.
I could even imagine a judge saying "this contract is a joke and not valid, so this work is implicitly copyrighted, as otherwise un-indicated works are".
>Dedicating works to the public domain is difficult if not impossible for those wanting to contribute their works for public use before applicable copyright or database protection terms expire. Few if any jurisdictions have a process for doing so easily and reliably. Laws vary from jurisdiction to jurisdiction as to what rights are automatically granted and how and when they expire or may be voluntarily relinquished. More challenging yet, many legal systems effectively prohibit any attempt by these owners to surrender rights automatically conferred by law, particularly moral rights, even when the author wishing to do so is well informed and resolute about doing so and contributing their work to the public domain.