My mistake. Looks like they license it from others.

To me it seems like it's impossible because they can't reorder bing search results or mixed them with other results. Or by their own admission because Google doesn't have a search API anymore. Unless I'm misreading. It's basically "Bing or Google wont allow us to use their products how we want to." And "It will take us over 20 years and lots of money to gain market share."

I'm paraphrasing here of course. But it doesn't seem impossible. I mean I don't think it's easy either. I also want to add that I don't want to live in a world with only one search engine.