From what I’ve seen, generally it’s assumed that the reverse engineering was done cleanly, unless there’s specific evidence to the contrary (i.e., explicitly copied code, references to leaked codebases, etc.).
This answer on StackOverflow is well-cited and goes into a lot of the US legal precedent surrounding these issues.
All that being said, if you’re profiting off of the work, you’ve entered an entirely different risk matrix.
From what I’ve seen, generally it’s assumed that the reverse engineering was done cleanly, unless there’s specific evidence to the contrary (i.e., explicitly copied code, references to leaked codebases, etc.).
This answer on StackOverflow is well-cited and goes into a lot of the US legal precedent surrounding these issues.
All that being said, if you’re profiting off of the work, you’ve entered an entirely different risk matrix.