Yahoo! has announced that they will begin charging developers for their use of BOSS. It won't take effect until sometime in the second quarter at the earliers. They also won't be charging for the first 10,000 API calls per day (depending on the call).
Yahoo! is also releasing SearchMonkey structured data to BOSS developers. Yahoo! gets this data by crawling microformats and RDF, which include embedded semantic markup. Now, API users can access this data.
BOSS was launched last year and it gives web developers the ability to build search engines for websites using Yahoo's search technology.
SearchMonkey was also launched last year to let site owners develop custom listings for search results. So far, several of these listings (aka apps) have been set to default in Yahoo's listings including Yelp, LinkedIn, and Wikipedia.