The Yahoo! Search Developer Network, announced yesterday, seems designed to go leapfrog a similar three-year-old offering from rival Google, enabling more API searches and more functionality.

The APIs will enable web developers to leverage Yahoo’s search service, as well as its image search, video search, news search and local search. APIs for related searches and spelling correction will also be made available.

The idea is that developers will be able to build search functionality into their applications, using a web services framework. The number of API calls participating developers can make each day is limited, however.

Yahoo said it will give each developer who signs up 5,000 calls per day, five times more than Google offers. Documentation and sample code written in Java, JavaScript, Perl, Python and PHP will be made available.

It’s not clear exactly what advantage such non-commercial programs offer companies like Yahoo and Google. In Google’s case, it has been a great brand driver, and may have helped the company locate developer talent.

Yahoo! Search Developer Network provides application developers with sample code and tools to share ideas and expertise, as well as the ability to showcase applications written and distributed by developers.

Yahoo has offered APIs for developers to plug into its Overture sponsored search brand (which was decommissioned yesterday, to be renamed Yahoo Search Marketing Solutions) service for a number of years.