Yahoo's BOSS platform, which lets external developers build custom search engines on top of the company's search infrastructure, will shift to a fee-based model in early 2011.

In its new version, BOSS (Build Your Own Search Service) will also give developers various options to generate revenue, and access to the platform will be based on the oAuth protocol, Yahoo said Friday.

BOSS, geared toward developers of all sizes, including individuals, startups and large companies, will provide access to general Web results, images and news articles, and its fees will be based on the type and number of queries from a search engine.

Yahoo will also make available a lower-priced BOSS version for academic institutions and non-profit organisations. Developers will get access to a dashboard to check their usage and charges, which they'll be able to cover via credit card payments.

It remains to be seen how developers react to having to pay for access to BOSS. "BOSS plans to provide full flexibility to blend, stack, and re-rank results. You know your users best, so we will give you the ability to display exactly what they need. We also aim to continue enhancing the BOSS offering by providing additional vertical search services in the future," wrote Rahul Hampole, a Yahoo senior product manager.

Yahoo, which is transitioning its back-end search infrastructure to Microsoft's Bing engine, will eventually also transfer BOSS to the Microsoft platform.

Yahoo plans to announce later a specific date for the availability of the new BOSS version, to which all developers must have moved 60 days after its launch.

After Microsoft and Yahoo announced their search partnership in July of last year, a cloud of uncertainty settled over Yahoo's search developer programs.

However, thanks to recent announcements, there is now a much clearer picture regarding which programs will not survive, such as Search Monkey, and what the plan is for those that will be maintained, like BOSS.

"It is a good sign for BOSS developers who may have suspected that Yahoo might end up killing it in light of the Microsoft deal. Putting together a monetisation strategy is a positive sign the technology will continue to be invested in," said IDC analyst Al Hilwa via email.

The Microsoft-Yahoo deal calls for Yahoo to rely on Bing for back-end search functions like Web crawling, site indexing and result matching and ranking. This transition is already live in North America.

Microsoft will also provide self-service sales of pay-per-click text search ads, while Yahoo will sell premium, guaranteed-placement search ads and handle individual relationships with the big advertisers, search marketing firms, resellers and their clients.