Details emerged today on Google’s broad social networking ambitions, first reported here in late September, with a follow up earlier this week. The new project, called OpenSocial (URL will go live on Thursday), goes well beyond what we’ve previously reported. It is a set of common APIs that application developers can use to create applications that work on any social networks (called “hosts”) that choose to participate.

What they haven’t done is launch yet another social network platform. As more and more of these platforms launch, developers have difficult choices to make. There are costs associated with writing and maintaining applications for these social networks. Most developers will choose one or two platforms and ignore the rest, based on a simple cost/benefit analysis.

Google wants to create an easy way for developers to create an application that works on all social networks. And if they pull it off, they’ll be in the center, controlling the network.

What They’re Launching

OpenSocial is a set of three common APIs, defined by Google with input from partners, that allow developers to access core functions and information at social networks:

• Profile Information (user data)
• Friends Information (social graph)
• Activities (things that happen, News Feed type stuff)

Hosts agree to accept the API calls and return appropriate data. Google won’t try to provide universal API coverage for special use cases, instead focusing on the most common uses. Specialized functions/data can be accessed from the hosts directly via their own APIs.

Unlike Facebook, OpenSocial does not have its own markup language (Facebook requires use of FBML for security reasons, but it also makes code unusable outside of Facebook). Instead, developers use normal javascript and html (and can embed Flash elements). The benefit of the Google approach is that developers can use much of their existing front end code and simply tailor it slightly for OpenSocial, so creating applications is even easier than on Facebook.

Applications can have full functionality on profile and/or canvas pages, subject to the specific rules of each host. Facebook, by contrast, limits most functionality to the canvas page, allowing a widget on the profile page with limited features.

OpenSocial is silent when it comes to specific rules and policies of the hosts, like whether or not advertising is accepted or whether any developer can get in without applying first (the Facebook approach). Hosts set and enforce their own policies. The APIs are created with maximum flexibility.

Launch Partners

Partners are in two categories: hosts and developers. Hosts are the participating social networks, and include Orkut, Salesforce, LinkedIn, Ning, Hi5, Plaxo, Friendster, Viadeo and Oracle.

Developers include Flixster, iLike, RockYou and Slide.

What This Means

The timing of OpenSocial couldn’t be better. Developers have been complaining non stop about the costs of learning yet another markup launguage for every new social network platform, and taking developer time in creating and maintaining the code. Someone had to build a system to streamline this (as we said in the last few sentences in this post). And Facebook-fear has clearly driven good partners to side with Google. Developers will immediately start building on these APIs to get distribution across the impressive list of hosts above.

And they’ll do it soon, too. It’s clear that the developers who arrived early to the Facebook Platform party won easy customers. Those that came later had to fight much harder. Developers found their new gold strike, and they will soon all be there, mining away.