Copyright protection comes into existence when a work is fixed in a tangible medium. Thus, copyright registration is not necessary to acquire rights in a work, but affords a number of benefits, including establishing a public record of the copyright holder's ownership, enabling copyright holders to sue infringers, allowing for statutory damages so that actual damages do not need to be proven, and enabling the copyright holder to prevent importation of infringing copies from other countries using US customs.
Copyleft is a colloquial term used to describe a free public license for use of an original creation.
Term of Copyrights For works created after January 1, 1978, copyright protection lasts for the life of the author plus an additional 70 years. For an anonymous work, a pseudonymous work, or a work made for hire, the copyright endures for a term of 95 years from the year of its first publication or a term of 120 years from the year of its creation, whichever expires first. For works first published prior to 1978, the term is different depending upon a variety of factors.