Not only that, a clean room isn't enough. You need to hire programmers straight out of college who have never looked at GPL code. Just kidding, it's even worse

Not only that, a clean room isn't enough. You need to hire programmers straight out of college who have never looked at GPL code. Just kidding, it's even worse than that - most developers right out of college have read at least one character of GPL licensed-code. Even stack overflow is tainted, because the questions and answers there were written by people who read GPL code. It's best to exclusively hire race car drivers and fedex delivery workers to your software development workforce, as they are statistically least likely to have been exposed to GPL code (per bureau of labor and statistics).