Jimmy Wales, the guy behind Wikipedia, is developing an open source search engine that will be ready for testing later this year. It would be nice to see some competition to the commercial engines, some of which have a bit too much advertising. An open source search engine might still need ads to survive, as the cost of indexing a portion of the Web and then dishing out results without bogging down requires a lot of hardware and even more electricity, to say nothing of a massive connection to the Internet.
The key difference between an open source search engine and a privately owned one would not be advertising, but in search algorithm transparency. There has been much speculation over the past several years that Google and other engines tinker with results to favor some sites and information. An open source search engine would be driven by search algorithms that could be examined by anyone, and so there would be full transparency of search results.