I think you're right that the term originates in hip-hop culture but when it was borrowed by imageboard culture it evolved into a descriptor of ideas and not of people - for the simple reason that imageboards are mostly anonymous.
Now when I see the term used online it's mostly in the imageboard sense of some idea or concept being 'correct' or 'agreeable' rather than the person who originates it. I think the term is undergoing a certain amount of semantic broadening too - more and more often I see it simply as a synonym for 'cool' rather than in the narrower meaning of 'this is controversial but I agree with it'.
I agree with that, but regard it as an evolution from my other answer meaning "established." The reference to contentious or unpopular comes because a based person has earned the ability to present unpopular ideas without repercussion.