Back in 2005 I wrote a Designer's Notebook column called "The End of Copyright," warning that copyright, as a property concept, is probably on its way out. It's a "right" that was invented out of nowhere after the invention of the printing press, and it will probably fade away some time in the next hundred years or so.
Or at least, the business model by which such innovations are exploited will change substantially, and making copies will no longer be considered wrong. (Oddly, I believe far more strongly in the European concept of moral rights than I do in copyright, but that's a story for another time.)
This time my ire is directed at gameplay patents. Patents are different from copyrights in important ways. They're a lot harder and more expensive to get (it often takes a year or more for one to be granted), and they don't last nearly as long. A copyright, under US law, lasts until the author's death plus 70 years, which means that an author's great-great-great grandchildren can still be raking in the bucks from a work they had no hand in creating.
For those created by a corporation, the term is 95 years from publication. By contrast, patents expire after 20 years... but even 20 years is a ridiculously long time in the video game industry. Furthermore, patents restrict any use of an idea, not just a particular expression of an idea as a copyright does. They grant much broader control over the invention.
To receive a patent in the United States, an invention must be new, useful, and non-obvious. A patent consists of a claim, or more than one, regarding an invention that the inventor wishes to protect. Usually a patent contains multiple claims for different possible variants of the invention.
For example, the Namco patent on load-time mini-games (US Patent Number 5,718,632), as originally used in the PlayStation 1 version of Ridge Racer, contains 16 claims, many of which are almost identical to one another. Each claim is a description of what was invented. The terms in this description are called the limitations of the claim -- that is, the boundaries of what is claimed.
Another device or process infringes a patent only when it contains every single limitation of one or more of the claims. If a single limitation of a claim is missing, that claim has not been infringed.
Unfortunately, however, most patents are written as broadly as possible, with large numbers of claims to cover various different ways of implementing the invention. This makes it difficult to avoid infringing a patent by making minor changes to the invention.