@lynne@pars.ee In the US, it's also legal to look at legally-obtained proprietary code and write your own (non-derived) code without an explicit cleanroom, legal defense is possible but more difficult. If I recall correctly, it was how NEC defended itself for using Intel microcode... Not applicable to leaked code, though.
Link for those interested
Somewhat related, 36 years later- NEC touts working with Intel on stuff.