When it's a complete rewrite anyway, just don't admit to use an illegal source code leak. I don't get why anybody would do that so openly. Just lie about it and claim it's a clean room implementation. That way if anyone ever were to prosecute this, they would first have to provide evidence that it's not clean room...
I wish we could live in a world where we could improve things freely…
Same here but sadly we don't and overly ambitious Sony lawyers could get the guy in serious trouble. That's why confessing to working on illegally leaked code is such a dumb idea.