A reminder on this topic that copyright does not protect ideas, inventions, or algorithms. Copyright protects an expression of a creative work. It makes more sense eg. with books, where of course anyone can read the book and the ideas are “free” but copying paragraphs must be scrutinized for copyright reasons. It’s always been a bit weird that copyright is the intellectual property concept that protects code.

When you write code, it is the exact sequence of characters, the expression of the code, that is protected. If you copy it and change some lines, of course it’s still protected. Maybe some way of writing an algorithm is protected. But nothing else (under copyright).