The “don’t even look at the code” take is very paranoid and probably only justified when the copyright holder is a litigious company so that you have a watertight defense in case you end up in court. It’s certainly not a legal requirement. As long as what you write isn’t derived from their code then you can put whatever license you want on it. If you haven’t even looked at their code then you definitely haven’t derived your code from theirs but you can look at their code and then write an unrelated implementation.
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