Trying OpenSocial once more.
There was a previous attempt at integrating OpenSocial into Drupal. My hope is this one will be more successful.
As it stands now the RESTful API aren't ready for but there's plenty of documentation to get an early start. I am planning on jump starting the server-based part of this project by evaluating the existing REST API.
Groups:
Login to post comments

REST Server
I put together the REST Server which uses the Services module to provides services to REST clients. It has been working quite nicely so far... How the Services module would integrate with OpenSocial is beyond me though.
No RESTful API just yet
As I mentioned, the OpenSocial RESTful API aren't ready yet. It seems we'd have to start with the JS API.
JavaScript API?
Dmitri put together the JSON Server, which will let you query services through JSON.
Use Shindig?
Why not use the Apache Shindig project to act as an app-server to drupal? Just have drupal track application data, but the actual processing of the apps can be run through Shindig....
Then all you need to do is write six replies to the standard app calls in the OpenSocial standard.