On the heels of social-networking sites such as Facebook and MySpace have come social applications, games, and services in the form of widgets that employ the data that users store and maintain on social networks. Since Facebook, the first company to open its doors to outside applications, launched its Platform last May, more than 20,000 applications have been built for the social network. Google, meanwhile, has been spearheading OpenSocial, a standard aimed at making it easier for applications to be used on multiple networks. Earlier this week, Yahoo announced its support of OpenSocial–which Facebook has not done–and joined Google and MySpace to form the OpenSocial Foundation, a nonprofit organization that the companies say would will be responsible for protecting the standard.

Joe Kraus, director of product management at Google, said in a press conference earlier this week that the foundation is meant to provide “safe harbor for intellectual property … by making it clear that OpenSocial’s use will be forever free and unencumbered, and to make sure that the OpenSocial Foundation stays community driven so that no one company ever has undue influence.” Kraus said that the companies plan to have the OpenSocial Foundation up and running in about 90 days.

OpenSocial is intended to allow developers to write an application for one social network and easily adapt it for another. In contrast, Facebook’s Platform requires the use of Facebook-specific programming techniques. Google announced OpenSocial last fall, and social networks including MySpace, hi5, and LinkedIn stepped forward during the following months to join in. So far, OpenSocial applications have only been launched on Google’s Orkut and on MySpace; hi5 plans to launch them on Tuesday. Between these three networks, Kraus said at the press conference, developers will have access to about 200 million users with a single application.

A Facebook spokesperson responded to the announcement by saying, “Facebook is a supporter of open source and sees value in any contributions the foundation may make to the industry. Facebook is not joining this foundation, but the company remains focused on advancing Facebook Platform to benefit the developer community and help users communicate and share information more efficiently.” Facebook has, however, begun working with Microsoft to allow people to use some of the data they’ve stored on Facebook in other contexts. Called Windows Live Contacts, the tool allows Facebook users to communicate with Facebook friends through services such as Windows Live Messenger, Microsoft’s instant-messaging client. “Facebook will continue to work with other trusted partners to explore new initiatives around data portability,” Facebook’s spokesperson said.

So far, Yahoo has given few details on the exact nature of its involvement with OpenSocial. Wade Chambers, vice president of platforms at Yahoo, said at the press conference that Yahoo decided to support the standard because it complements some existing Yahoo tools, such as the photo-sharing site Flickr, and developer tools, such as the Yahoo User Interface library. Chambers also pointed to Yahoo’s support of other standards, such as OpenID, which allows users to maintain log-in information that works on multiple sites.