Earlier quoted context omitted.
Here's the thing though: suppose you have worked for some previous employer, and seen their proprietary codebase. By your logic, you'll never be able to work on anything else or for any other employer without being a legal risk to them. I do not think the chances of me implementing something so similar to something I have read before such that it would constitute copyright infringement are very high. I usually can't…
The code I see from my employer is indeed a risk to my employer later on, but at least I'm seeing this code legally . Whether or not this makes any sense, I don't know. I'm also not a lawyer, but I believe this principal is important for clean-room reverse engineering as well.
And yes, clean room design is a bit more extreme in that regard (which is probably something companies/individuals do if they expect a high risk of litigation, as it probably makes it a lot easier to prove that there is no copyright infringement, and certainly not willful infringement)
So, the requirement for Wine and ReactOS mentioned in the other comments is probably not unreasonable.