In a bid to counter Google, Facebook is going open-source.

A year after its launched its much-heralded Facebook Platform – a way for third party developers to write programs that work inside the social network – the Palo Alto, Calif., company says it is making a “significant part” of its platform code open-source.

That means developers and companies working in the Facebook ecosystem will be able to see how the code works, manipulate it and give any improvements they make back to the company and other developers.

“The goal of this release is to help you as developers better understand Facebook Platform as a whole and more easily build applications,” the company said in a statement. “We’re also hoping you use Facebook Open Platform in ways we’ve never thought of.”

Though it is posing the announcement as something of an altruistic gift, there’s a bit of a chess strategy behind Facebook’s move. Google launched the competing Open Social initiative last November, a common set of software tools that developers can use to write programs for a variety of social networks, such as MySpace and LinkedIn.

Open Social gives Facebook some formidable competition for the hearts and minds of developers, whose work is seen as integral to making social networks a fun and enduring place for people to spend their time on the Web.

“Developers and users are fickle. They are going to go where barriers to entry are the lowest,” said Jeremiah Owyang, an analyst at Forrester Research. Facebook, he said, “needs to continue to build relationships with these developers or it is just going to be one of many platforms.”