[throwawaykf02]

It's not really double protection, because patents and copyright cover different things. Copyright only protects the exact expression of what some software does. Patents cover the functionality of that software. In fact, since software per se is not claimed, the claimed functionality could be implemented entirely in hardware and still be covered by the patent.

No amount of copyright can protect the functionality, because 1) there are countless ways of implementing the same functionality and copyright only protects your specific way, and 2) copyright cannot legally cover functionality anyway.

As such, providing source code in a patent is of little value. (Although I have seen patents containing source code.) As long as you can reimplement the method being claimed by reading the patent with little undue experimentation, it has met its "enablement" requirement.