Facebook is to help other social networking sites to run applications developed for its own software platform.

The company already encourages developers to build applications that work with its site, publishing details of the tags and APIs needed to exchange data.

Now it plans to license those details for use by other social networking sites and platforms, according to the Facebook Developers blog. The idea is that developers will only have to write their widget or small application once if there is a common platform for structuring how the applications integrate with sites.

The initiative runs in parallel with Google's OpenSocial project, which revolves around creating standard APIs for social networking applications. APIs let applications exchange information and are crucial to building programs that, for example, take information from Facebook profiles and blend it with some new functionality or feature.

Facebook already has a taker. On Wednesday, social networking site Bebo said it would use Facebook's standards for its own Open Application Platform. Bebo isn't taking sides, however: it will eventually support Google's OpenSocial too, it said.

MySpace, the largest social networking site, has also said it will support OpenSocial.

Facebook said its architectural platform is composed in part of HTML-related tags and methods for building applications.

It published details of FBML, its set of tags for formatting data exchanged between applications and users. Some of the tags enable developers to build programs with the same design elements as Facebook's site, so the application blends in.

External developers have created about 7,000 applications since Facebook opened up its site in June. The applications have offered a commercial opportunity for developers, although Facebook has been under fire for how those programs respect users' privacy.

Google's OpenSocial platform got off the ground last month with Plaxo's Pulse, the first application to use the APIs. Pulse, which aggregates and delivers new information from social networking and other webites, is a feature of Plaxo's web-based address book service.