You say you’re feeling down, bunky, because everyone seems to have a Facebook app but you?  Well, got a web site?  Then, perk up, son!  Because you are well on your way to having a social app — one that’ll actually run on a whole bunch of social networking sites that have at least as much traffic as Facebook — and maybe even on Facebook itself soon. At least that’s what Marc Andreessen, founder of social-networking platform Ning, has to say on his blog post today.

It’s all thanks to the "Open Social" spec set to be announced tomorrow by Google, which says it already has about a dozen partners, including Hi5, LinkedIn, Ning,
Friendster, Salesforce.com, and Oracle. See this Wall Street Journal story (actually dated tomorrow!) and this one in the New York Times, which was published today.

So, how can you transform your web site into an "Open Social" app?  Andreessen says it’s even easier than developing a Facebook app. He says you "just take your current HTML and Javascript front-end pages and create a version of those pages that use the Open Social API."

Andreessen believes web site owners will soon begin maintaining multiple sets of front-end pages for their web sites, in order to get "maximum distribution across the largest number of users." And he says it’s easy. They’ll have a single back-end, but multiple sets of front-end pages.  Here’s how he defines what those multiple sets will be:

• One set of standard HTML and Javascript pages for consumption by normal web browser.
• Another set of HTML and Javascript pages that use the Open Social API’s Javascript calls for consumption with Open Social containers/social networks.
• A third set of pages in FBML (Facebook Markup Language) that use Facebook’s proprietary APIs for consumption within Facebook as a Facebook app.
• Perhaps a fourth set of pages adapted for the Apple iPhone and/or other mobile devices.

"The overwhelming good news here," said Andreessen in his blog post, "is that these pages can all be served and serviced by the same back end code."

I think this "Open Social" spec is big news.  It’s something I know a lot of insiders have been been thinking about, at least in the back of their minds, since the Facebook juggernaut took off some five months ago.  Walled gardens — proprietary platforms — just don’t last on the Internet. Like my buddy PXLated said in a previous comment, "The Internet just routes around ’em."  Indeed.  Let the party begin….

UPDATE (11/1):  Marc Andreessen did another very informative blog post with a screen cast and screenshots showing how the Open Social spec can be implemented, using three actual Ning social networks as examples.