and the same discussion on being able to get a patent on APIs also happened - the most famous contestant at that time was Microsoft's .Net API patent applicatio

and the same discussion on being able to get a patent on APIs also happened - the most famous contestant at that time was Microsoft's .Net API patent application (now US7581231) - by now MS hold a series of patents on other APIs plus has a whole lot of additional API patent applications pending. Now one could say that there are many patents that should have never been granted to MS or others (one of the better examples for MS would certainly be getting a patent on a Windows sudo implementation - US6775781) - but it might be indicative why MS went along the path to get patents on APIs vs trying to just copyright it. Given that copyright protects the form of expression rather than the subject matter itself this pretty much explains why the copyright office would only require the first and last 50 lines of code. While the answer with e.g. REST APIs that are pretty much exchangeable might be rather easy with more complex ones like system level or also the Java API this becomes pretty complex. Maybe an analogy might help: If you take a car you might be able to patent and copyright most parts and functions but you certainly will not be able to copyright that you can drive the car per-se. With an API like the Java API where the majority has been open sourced the actual use of the API (IMHO up to the wording of it or making this wording available in your application) is merely the general ability to use the solution overall - like diving a car or making it possible to drive along with other cars in traffic. Then comes the question if Sun / Oracle have actually previously provided the permission to use the API directly or as part of other licenses (e.g. ClassPath)