Let's compare this to a completely different field: cookbooks. Recipes themselves aren't copyright protected. However, specific instructions for the recipes ar

Let's compare this to a completely different field: cookbooks. Recipes themselves aren't copyright protected. However, specific instructions for the recipes are protected. In addition, though individual recipes aren't protected, a collection of recipes is protected. There is a line, though, between copying a few recipes, and an entire collection. That line is not easy to define, but that doesn't preclude the existence of such a line. So – is an API considered a single recipe? Or is it a "recipe collection?" That seems to me to be an important distinction. If you were to copy one set of API function names that cover a limited area, then it could be argued that you used just one "recipe" and that it would be OK. However, if an entire collection of API function names across a very broad range of categories was copied, then it is harder to argue that you didn't copy any entire collection, and not just an individual recipe.