I just heard that Oath have released the Vespa Search Engine open source. When I was in Yahoo! it was used for everything. I predict that a company will exist in a few months selling it as a service.
I think Vespa was one of the be best written pieces of infrastructure at Yahoo! that I worked on. It was well documented for an internal app and it was blazingly fast. The guys working on it were also super smart. I will be interesting to see where it goes but I think it will be a contender in the search space.