It looks inevitable that Facebook will move away from its proprietary platform to the open platform of OpenSocial. Indeed, sources tell me that representatives from Facebook and Google (GOOG) met for the first time late yesterday afternoon. And already, Facebook investor and board member Jim Breyer is indicating that the social network would be willing to join the Everybody-but-Facebook Alliance.

Meanwhile, a favorite parlor game yesterday afternoon among pundits here in Techland was playing “What Should Facebook Do?” — though most of the people I spoke to were unwilling to go on the record. Virtually everyone’s answers however, boiled down to three options:

1. Do nothing. Facebook has a surprising amount of power in this relationship. It has 50 million members and continues to grow. As long as that’s the case, developers will continue to craft apps in FBML, its proprietary platform language.

2. Surrender, totally and at once. Converting Facebook’s platform to open HTML isn’t difficult from a programming standpoint or particularly time-consuming. Besides, developers will love it. Many have privately griped that Facebook’s platform is too gnarly and they look forward to simple HTML and Javascript. And no one I’ve spoken to can find any real problem with this shift from Facebook’s perspective — indeed, the move should benefit Facebook since its members will be able to stay put, where FB can serve ads at them, while doing more outside the walls of FB.

3. Some combination of 1 & 2.

One person who was willing to go on the record was John Lilly, COO of the Mozilla Corporation, whom I had dinner with last night. Who better to talk about the virtues of openness? Lilly, in fact, made me think that Option 3 was the smartest way to go. If he were running Facebook, he said, “I would not let Google take the ‘open’ mantle from the world.” He said that if Facebook decides that it needs to move from FBML to HTML — “and I’m not saying I’d necessarily do that if I were Facebook.” But if he did, “I’d cause Google some problems first.”

How? “If I were Facebook, I wouldn’t let Google say, ‘We are the Web.’ I’d call b.s. on them,” Lilly said. OpenSocial isn’t open! It’s a Google-run alliance; Google is calling the shots and is in charge of running the thing. But that’s kind of bogus since theoretically, it could cause OpenSocial to move in ways that benefited it. True open standards initiatives tend to be run by open boards.

Of course, the down side to working with open-standards boards is they tend to move very slowly. Google is known for having little patience for that sort of thing.

One person I spoke to, who asked to remain anonymous because he is close to the current action, said challenging Google on whether OpenSocial was truly open was a red herring: “It’s a false challenge,” this person argued. “Even if Google has significant control over the API, the way it’s inevitably going to get controlled in reality is by the interoperable implementations that that people actually use. Interoperability itself will be the glue that keeps it from becoming proprietary. This is a dynamic that has worked very well for Internet standards over the years including HTML, HTTP, and TCP/IP itself, despite some very large and dominant vendors who would have preferred to take control of things like those. ” He also referenced this Anil Dash piece, which provides all the ammo you need to support the inevitability of Option 2.