It is a fundamental feature of copyright law that it protects
only original expression, not ideas. Applied to software,
the law of copyright tells us that certain elements of a computer
program are not protectable by copyright. For example, purely
functional elements such as the structure of a library, or
database, or elements dictated by the operating system, can fall
outside the scope of copyright protection, since those elements
lack the originality necessary for copyright.
In Tetris Holding LLC v. Xio Interactive, Inc.,
an app developer was found to have infringed copyright in the
famous Tetris game. The puzzle game Mino
was, by the defendant's own admission, inspired by
Tetris. However, the defendant maintained that it only
copied unprotected elements, a conclusion that the developer
reached after researching copyright law. The court did not agree.
After an exhaustive review of the idea-expression dichotomy
(40-pages worth of anaylsis, if you want to read
