They sell API access to Google searching.

Microsoft sells Bing to a ton of search engines, it has been the go to for everyone who wanted to run a search engine.

Ecosia have also been relying on Bing, but recently announced that they've now added Google as well.

Bing index has always been licensable , Yahoo was using it too, and they have other customers .

I don’t think Google has a publicly known licensing deal ,