> If one of your engineers has to download and study the leaked source code, they've infringed Nintendo's copyrights.

Is this an accurate interpretation of copyright law? I thought copyright was meant to prevent books from being copied, not to prevent books from being read.

I'm quite confident it's accurate. Downloading is copying. Downloading leaked proprietary source-code infringes the copyrights of the holder. That's as it should be.

If you download a commercial ebook from BitTorrent without having paid for a licence, that's copyright infringement. Nintendo chooses not to put its source-code on the market, so you have no means of acquiring a licence to it. Downloading their copyrighted work in the absence of a proper licence, and in the absence of an exception like fair use (I really doubt that applies here), is copyright infringement, almost by definition.

Not exactly. Copyright covers redistribution, not viewing someone else's illegal copy. That's why you can get a DMCA notice or copyright strike for uploading, torrenting, or hosting copyright works but not for downloading them. (Why torrenting? See below)

When you get sent a DMCA or copyright strike for torrenting movies, their legal basis isn't that you downloaded the content but that you then seeded it to peers. This is also why Popcorn Time etc. (can) generate strikes, because you also serve as a seed and redistribute content to other users.

Otherwise, the MPAA would have a field day with this and strike anyone who used an illegal streaming site. Watched a leak on Dailymotion? Strike one. Watched a clip of a show on an unofficial YouTube channel? Strike two. etc.

This is not true. The law governs humans, not computer technical details.

https://en.wikipedia.org/wiki/Download#Copyright

The reason uploaders are prosecutor more is that they are easier targets (more evidence, more damages)

DMCA takedown copyright strikes are one specific part of copyright law, that applies to hosting services and safe harbor protections for them. There is much more to copyright law.

You've used the word "prosecuted", not "sued".

Copyright infringement tends to be a civil thing that rights holders can sue for loss of earnings, rather than a criminal thing that the police will prosecute.

In some jurisdictions the civil wrong can be tipped into a criminal offence. In England if you infringe copyright as part of a business that would be a criminal offence.

I've read that streaming might be legally different, as it might not legally qualify as making a copy. It's difficult to find a reputable online source directly answering this question. I imagine the answer might vary between jurisdictions.

Streaming definitely counts as making a copy, it is functionally the same thing as downloading the media. Search your ram/HD and the file is there. I've never heard of anyone prosecuted just for downloading though, which is what I'd guess started this rumor.

I thought it was simply that uploaders get charged with distribution which carries a stiffer penalty or something. Like the difference between getting charged with drug possession and drug trafficking. How getting caught with drugs, unless in massive quantities, will have less steep punishments than getting caught with a bunch of drugs, scales and baggies.

At least in the cases i've heard of. It could be one of those old wives tales kind of things though. I honestly don't know.

It is (un?) fortunately impossible to tell whether someone obtained some knowledge from leaked source or by reverse engineering. Especially when looking at assembly (or RE through other methods) could in theory produce the same bugs/quirks as the original.

Sure, but I was speaking to whether it breaks the law, rather than whether you're likely to get caught. If you don't care about the law, why bother to go halfway to the clean-room methodology?