Making system/library calls to display something on the screen does not necessarily require the use of an SDK either; it might require quite a bit of reverse en

Making system/library calls to display something on the screen does not necessarily require the use of an SDK either; it might require quite a bit of reverse engineering work. As far as I understand copyright, that doesn't involve copying/distributing the library code and wouldn't be legally encumbered unless there's a patent covering it.