Open source search engines allows anyone who desires to make changes for the improvement of the software. It is an approach to contribute improvements and additional functionality to the software.
There are several open source search engines available to download and use. Here is the list
Google Knol, is a user-generated encyclopedia, collaborative reference site. It’s similar in concept to Wikipedia, except that Knol allows its authors to earn a profit from their articles with ads.
“Our goal is to encourage people who know a particular subject to write an authoritative article about it,” according to Google.