But I think you've got a couple of holes in your simile. Source code is a much more powerful thing to have than the final product. I can't remember a time where a movie's entire set of footage and effects assets were leaked/stolen, and the equivalent of a movie being leaked is compiled binaries being leaked, and that happens all the time. I'd also judge selling an illegally copied thing to be a worse offense than giving away an illegally copied thing.
> Certainly company B let company A keep its source code, but by copying the source code it did not let company A keep its way of earning money.
And yet, companies still make software, movies, music. I'd be more worried if those businesses were made non-viable due to copyright infringement losses and more sympathetic if I thought something copyrighted today would exit copyright within my lifetime.
But there are circumstances that might mitigate how the public (and perhaps law) feels about that, eg, if company B bought a copy of the software and slightly modified it to work on a new operating sysem, then sold just the changed version.
What if the copyrighted material was code instead of media?
Suppose company A invests $500M in writing code for a major new product. Development finishes and they begin selling the product and slowly recouping their costs. Now, company B comes along and surreptitiously hacks into company A, copying their their source code (they haven't stolen the source code, only copied it). Company B now begins selling a copycat product for far less than A wants to charge, destroying A's ability to earn back its investment. Has company B committed a crime?
Certainly company B let company A keep its source code, but by copying the source code it did not let company A keep its way of earning money.