IANAL, this is not legal advice. Linux and OS X implement the same APIs as Unix. Windows implements the same (or very similar) APIs as PM in OS/2. Most modern

IANAL, this is not legal advice. Linux and OS X implement the same APIs as Unix. Windows implements the same (or very similar) APIs as PM in OS/2. Most modern PCs reimplement the IBM PC "API", hence "PC compatible". > In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work. (—Copyright Law of the United States[2]) APIs are the idea that binds components together. Even if you come to understand the interface by reading a programmatic description of it (e.g., a function signature), and reimplement it, and your language forces you to use the same exact wording to match the signature (b/c it's an API), there's nothing different here than the same exception given to the way that a the raw listing of ingredients in a recipe is not copyrightable (and this is called out as an example of such by copyright.gov[1]). The appellate court erred in its application of the law. Additionally, this was said on one of the amicus briefs, > reversing the District Court would dangerously undermine the settled expectations of computer scientists and the entire computer industry that rely upon the open nature of APIs (—Martin Fowler, Bruce Schneier, Bjarne Stroustrup, et al. were signatories to this amicus brief.) The decision, were the industry to actually pay attention to it, would wreak havoc on the state of software engineering. [1]: https://www.copyright.gov/circs/circ33.pdf https://www.copyright.gov/circs/circ33.pdf [2]: https://www.copyright.gov/title17/title17.pdf https://www.copyright.gov/title17/title17.pdf