It means that you should acknowledge the culture of the people who started it, not too much more than that?
It can get dicey and weird at times, and there's a lot of details that one could get into, and that's good homework to do -- but I definitely find that the vast majority of popular white rappers do a good job of this, e.g. Eminem.
what constitutes the start? DJ Kool Herc? If you asked him, he would list his influences and predecessors... do they not count ? If you try to demarcate some sort of cultural "break" where X becomes Y, how do you do that? And how do you handle subsequent cultural "breaks" that presumably, by the same logic, create something new. How do you handle parallel flows that then converge (such as electro-funk evolving under the influence of kraftwerk, and then becoming the first thing actually named "hip-hop") ?
This is all nonsense. Culture is not "owned".
Almost all the best culture in the world is mongrel culture that arose from someone who grew up in one culture(s) being exposed to other cultures and mixing them together in a way that generally reflects as much upon the individual as or more than the source cultures.
Hip-hop is no different in this respect to any other form of human expression. If there's an art form that seems "pure" to you, the most likely explanation is that you haven't gone far enough into the past to understand how it is also just another mongrel form.
It can get dicey and weird at times, and there's a lot of details that one could get into, and that's good homework to do -- but I definitely find that the vast majority of popular white rappers do a good job of this, e.g. Eminem.