Bebo already licenses access to the Facebook Platform so how it can be done is already visible. Under the new scheme ANY social network will be able to provide support for Facebook apps on their own site at no charge.
I opened the post with a question but I’m going to answer it by suggesting that while there is zero doubt that this move by Facebook is a direct response to Google (and reactionary moves are never brilliant) the depth of applications on the Facebook platform will likely see a slew of mid to low range social networks rolling out support for this.
The down side: we are now seeing a social networking cold war where various parties are lining up behind Google and Facebook, with some trying to remain neutral. Will the stand off benefit users? Unlikely, but the future of the biggest game in town is at stake, so expect both sides to further up the ante as the stand off continues.