Not to take you two steps back but copyright doesn’t really apply well to software to begin with. Consider this:
Copyright applies only to creative expressions. Purely functional expressions are not copyrightable.
That means that software is the embodiment of both creative and functional expressions that are commingled. They are so mixed together by the time the buyer gets it, there is no simple way of separating the two. That weakens the strength of copyright over the whole.
It also misleads folks into believing everything about software is protected, even silly things like header files or trivial functions. Because these purely functional expressions are so highly intertwined with the rest, folks just assume they have a legitimate copyright over them! Even judges get this wrong!
So software isn’t inherently copyrightable except for it any creative expressions it contains. What counts as creative expression?
Traditionally, it didn’t take very much creative expression to be copyrightable. A screen design is copyrightable. A color scheme could be copyrightable. Code that saves a file after applying whatever edits the user has made is NOT copyrightable, as it is a purely functional expression.
But what if I came up with a cool/fast way of finding primes and coded it into C. I created it. It is unique in the entire world! It took many hours to come up with. Certainly I should be able to protect my work, right?
No. Mathematical algorithms are not creative expressions but purely functional expressions. It doesn’t matter how long it took to create or how the algorithm was discovered.
But what about the code to implement the expression? The code is the expression of the algorithm. There may be a bit of creativity in the code, but we are back to functional expression as opposed to creative expression. Where’s the line? It’s fuzzy enough considering it in the abstract but impossible to consider given only the executable software itself.
Personally, I think software should have it’s own copyright protections, unique from other written works. What that should look like and how it should work is an open question that should be discussed.
Remember, the purpose of copyright is not to enrich the author. The purpose is to “promote the progress of science and useful arts, by securing for limited times to authors and inventors the exclusive right to their respective writings and discoveries.” If any copyright scheme fails to “promote the progress of science and useful arts”, it is not serving the public as intended.