Earlier quoted context omitted.
Never, ever, ever, ever worry about anyone copying your stuff. Depend on your unique insight. No one can copy that. If in the extremely rare circumstance that someone copies you, be thrilled! That means you are building something valuable (which is extremely rare).
This is bad advice. If you have a really good idea and a company in the same space with the money and resources to beat you to market sees it, it's very possible they will bring it to market before you. Large companies like Google and Facebook will regularly feign interest in someone's app or idea (that they might want to purchase), only to roll it out themselves.
That's the whole point of the advice: stop worrying about being copied. It's a fake problem.