From the article:
"I know for a fact that Wikipedia operates under a CC BY-SA 4.0 license, which explicitly states that if you’re going to use the data, you must give attribution. As far as search engines go, they can get away with it because linking back to a Wikipedia article on the same page as the search results is considered attribution.
But in the case of Brave, not only are they disregarding the license - they’re also charging money for the data and then giving third parties “rights” to that data."
Of course, using add-ons also requires diligence, as each add-on from each source requires one to both trust the source and vet each source regularly. An add-on is also as trustworthy as the people that made it, and one must be willing to do the work the verify that those add-ons continue to be safe.