Quote - They are copyrightable, but like computer programs, there are some subtleties invovled in determining what is covered and when or if something may have been derived from something else.

In software there are parts that are copyrightable and parts that are not copyrightable, if a parts is not copyrightable it doesn't matter if is a derived work or an exact copy, this part is not subjected to copyrights.
For example, in most of the Windows executables (exe or dll) the first 128 bytes are exactly the same.

Stupidity also evolves!