The Objectives of the Copyright Law
Copyright exits to induce people to make creative works. The law rests on an assumption that, without legal protection against copying, authors and publishers would under-invest in expressive works such as books, movies, music, and software. By granting an exclusive right to copy and distribute, the law insulates copyright holders from competition by low-cost copiers who did not incur the expense of creation and production, and thus offers an incentive to others to invest in these activities.
In economic terms, copyright law is justified by the "public goods" nature of creative expression. A public good is one that is both nonrivalrous (multiple parties can possess it simultaneously without interfering with one another's possession) and non-excludable (once released to the public, its creator cannot physically exclude others from accessing and using the work). Economic theory predicts that, without some legal means to limit the use of such goods, the public would attempt to free ride by taking the good without contributing to its production costs. Creators, unable to capture the value generated by their works, would fail to produce works whose net benefits outweigh their cost, resulting in a classic market failure. Essentially, copyright law gives creators the legal right to demand payment from those that use their works in certain ways, which facilitates markets for such works and, hopefully, provides an engine for creative production. At the same time, copyright law expressly allows for fair use of copyrighted works by educators, commentators, and other whose use, on balance , benefits the public and does not threaten copyright holder's core economic markets.
In the early 20th century, the right to copy included only human readable forms, US congress amended the Copyright Act to give authors rights over mechanical reproductions of their woks, in forms such as piano rolls and records, but Congress added a compulsory license that allowed competing manufacturers to sell recordings of music as long as they paid a fixed fee to the music copyright holder. This so-called mechanical license is still in effect, along with more recently enacted compulsory licenses for activities such as cable and satellite broadcasting.
Vicarious and contributory liability
The Copyright Act of 1976, gave copyright holders the exclusive right to copy, to distribute copies to the public, to perform or display works publicly, and to create adaptations or modifications of the copyrighted expression. Others who benefited indirectly from these activities - such as manufacturers of printing presses, record players, and other technology that people occasionally used to infringe - were free to sell their products without interference from the copyright holder. Copyright law reached only two narrow subsets of people who did not themselves infringe: those who controlled and profited from direct infringers' behavior and those who actively helped others to infringe. These forms of liability - called vicarious and contributory liability.
Peer-to-Peer technology poses serious challenges to copyright
Before the late twentieth century, in the pre-Internet age, creative content was distributed in physical copies whose creation and dissemination required substantial investment. P2P technologies empowered individual users to distribute content files without any centralized gatekeeper, and without any personal profit motive, much of the public views it as more akin to personal use than to infringement. Although this threatens to displace legitimate sales of those products in the same way that pirated hard copies did in the past, but locating and pursuing its perpetrator is no easy task. Therefore, Peer-to-Peer technology poses serious challenges to copyright.
US Federal law requires that the work be stored in some "tangible medium of expression" which includes machine-readable forms, and while the law excludes "ideas, processes, and methods of operation" from the subject matter of copyright, protection extends to many expressive aspects of functional works, including most forms of computer code.
the Evolution of Copyright Law
Copyrighted works currently receive protection for an extraordinary length of time: the life of the author plus 70 years for individually authored works, and up to 120 years for employee-created works.
The 1909 Copyright Act provided for a 28-year term, which could be renewed for another 28 years.
Before the 1976 Copyright Act, United States copyright law required that copyright holders publish, register, deposit, and give copyright notice on their works as a condition of legal protection. Copyright holders also had to request a renewal of their 28-year copyright, if they wished to enjoy rights for the full 56-year potential term.
After January 1, 1978, all copyrighted works enjoy the life plus seventy year term.
With the growth of personal copying technologies such as photocopiers, VCRs, and cassette tape recorders, copyright holders complained that individuals were committing infringement with these technologies, and that those who made and sold the machine should be held to account. But the Supreme Court held that the sale of copying equipment, like the sale of other articles of commerce, does not constitute contributory infringement if the product is widely used for legitimate, unobjectionable purposes.