The Google Adsense program offers publishers several different ways to add Adsense advertisements on their site. The two most popular and commonly used formats are in-page contextual ads and ads on Google powered search results page.
Today the Adsense team announced that publishers who employ a home grown solution to offer search feature on their sites can embed Adsense ads on their search results page too.
We understand that some of you may have your own, non-Google search results that you'd like to monetize. In the past, this typically meant that you weren't able to use AdSense for search ads. Now, with AdSense for search ads only, publishers can now include AdSense for search ads on their pages and pair them with their own, homegrown search results.
Until today, Adsense on search results page was available for only those publishers who uses the Google Custom Search tool to provide search feature on their sites.
AdSense for Search Ads Only is currently available only on a request basis. If you are interested, you should fill this form and wait till Google responds.