Yahoo held Open Hack Day October 5 and 6 in Bangalore, India, in a bid to build an ecosystem of external developers familiar with the company's technologies.

The event follows similar ones in Sunnyvale, Calif., in September last year, and London in June. Before that, Yahoo used to have internal hack events for its own staff.

After the Open Hack Day in Sunnyvale, one participant started a company based on an idea that came to him at the event, David Filo, Yahoo's co-founder, told reporters Saturday in Bangalore.

Yahoo needs the ecosystem to come up with ideas that may not come from within the company, said Bradley Horowitz, vice president of Yahoo's product strategy group. Any intellectual property (IP) developed at the hacker event is the property of the developers, he added.

About 500 developers had applied to participate in the event, at which Yahoo provided the infrastructure, food, and rock music for the attendees, according to Horowitz. The number of participants was however limited to 200 due to space at the venue, and also because the developers were screened to ensure high-quality work at the event, he added.

Yahoo opened the APIs to some of its products such as Yahoo Maps, Yahoo Search, Flickr, and Delicious to developers, Filo said. "From a Hack Day like this, we get an idea of which other APIs it would be beneficial to open, to create an ecosystem of technology development around Yahoo technology," he added.

Applications displayed at the event included YaHealer, an application that allows doctors to share photos of a brain scan over two Yahoo widgets that are connected over the Web, and change in sync.

A number of multinational technology companies, including Google and Microsoft, hold events and contests for developers in India. In some cases, these have been opportunities to identify potential recruits for their development centers in the country.