Facebook is releasing as open-source software parts of its application development platform in order to make it easier for programmers to create applications for the social-networking site, the company announced Monday.
Facebook will offer as open source "most" of the code that runs its platform, plus implementations of its most popular methods and tags.
This is another step in Facebook's program for external developers, which it kicked off a little over a year ago when it opened up its platform to them. Since then, about 400,000 developers have created some 24,000 applications for Facebook.
With this move, Facebook is also responding to Google's OpenSocial, an initiative to establish a standard set of common APIs (application programming interfaces) that will let developers create social-networking applications that can run with minor modifications in multiple sites.
OpenSocial is generally considered a challenge to Facebook's platform, because observers believe it could make it easier for social-networking sites to match Facebook's broad catalog of third-party applications.
Among OpenSocial's supporters are Yahoo, AOL and MySpace, Facebook's biggest competitor. In March, Yahoo, Google and MySpace formed a nonprofit foundation to promote the OpenSocial platform as a neutral, community-governed specification.
With the open-source portions of its code, Facebook expects that developers will find it easier to test and tune their applications, and create their own tools, among other things.
The Facebook Open Platform, or fbOpenn, as the open-source portion of the platform is called, can be extended so developers can create their own tags and API methods, Facebook said.
The open-source portion of the platform includes the REST API, FBML parser, FQL parser, and FBJS sanitizer and proxy, Facebook said.
Most of the open-source code is being made available via the Common Public Attribution License (CPAL), while the FBML parser is governed by the Mozilla Public License (MPL).