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 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. It will be interesting to see where it goes but I think it will be a contender in the search space