Copyright as a concept hasn't changed for hundreds of years. Copyright law itself has changed dozens of times in the United States. But the fundamental principle of copyright is protecting the "copy right" of authors, this has been immutable over the years. Copyright's most important stipulation is that only the owner of a copyright controls the legal ability to produce a tangible copy of a work. This is typically done for profit. It is believed with strong conviction that such a system can only enhance the creation of works protected by it.
Yet copyright has changed so much since the creation of the Internet, without even a word having to change in copyright law. Copyright has become very hard to enforce, hard to not violate, and it turned into a law that applies to everyone universally.
The "copy right" is no longer easy to enforce because computers are copy machines by their nature and the Internet makes distributing these copies to a wide audience of interested consumers very easy.
The Internet and computers has turned everyone into a possible violator of copyright. Recall from my previous post that the copy machines of old, the printing presses were very expensive and hard to operate. Only a subset of business really owned these machines, these businesses are called "printers" or "publishers". Copyright largely only concerned them. If they didn't like copyright universally, they are still such a minority of the greater population no one cared. There is no way to violate a copy right when you lack the ability to make copies!
Now everyone with a computer has the most advanced printing press ever invented, as good as what the major companies have. The ability to copy conveyed by computers is post-scarce, everyone has can make perfect copies of anything that can be conveyed in information and no one really has this capability better than anyone else. So we live in a world where everyone is potentially a copyright violator. And it's a law that amazingly easy to violate, even if you don't try to. Even the hardline proponents of copyright law have been caught violating it.
All this has led to a once largely uncontroversial law possibly being the single most controversial area of politics in existence.