Interesting points! I am not sure which is right, or legal, but there seem to be grey zones, yet.
> Another red herring here... it is irrelevant how superficially close this is to the original source code.
It wasn't until Apple vs. Franklin that object code became copyrightable, prior to that the USPTO held the analogy of "design drawings vs. actual bridge" as the relation of "source vs. object code", and as far as I am aware that case still left some questions open.
There's also the first sale doctrine. So, once I buy a (mechanical, haha) car, I can modify it, take measurements of it, in fact describe and publish every bit of information I can think up of, right, because once it was given to me, I can do with it as I please, unimpeded by the manufacturer. This is, of course, where things get murky.
Now, a binary has elements of literal nature that copyright protects, but a decompilation results in a completely different information stream, so that seems like a non issue. Thus, we are left with the non-literal copyrightable elements of structure, sequence, organization. Copyright protects expression, but not ideas. So, the binary code is an expression of the author's ideas, and thus it seems sensible that the decompiled version is, too, BUT: only creative expression, not things that are necessary and utilitarian to perform a given function, and this is where it get's less well-defined. So if there are decompiled portions, that might not be enough for a copyright claim, provided they are utilitarian in nature. Of course, just decompiling the whole thing and publishing that looks very much like infringemen, indeed.
I do think this nicely embodies the difficulty of dealing with IP vs. actual, tangible things, though. With the car or bridge analogs, copyright would not prevent anyone from replicating them, but it would be patents and trademarks that put restrictions on how and what can be reproduced, instead of the much stronger restrictions of copyright on software.
I'd personally much more comfortably equate binary code with mechanical elements than works of creative authorship (though much of my livelyhood relies on the latter, in lieu of other mechanisms), but this view isn't universally shared, and possibly not even universally applicable.