It's all in the documentation - it is possible but very slow. OpenSocial is not perfect, and Ning's implementation of it is incomplete and out of date. I did manage to get my own php/mysql app running on a network through opensocial but the members hated it because randomly it wouldn't load, or would take ages to load. I'm not the world's best programmer, but this just wasn't a practical solution. Too many round trips from servers to other servers, back and back again! Even Ning admit their implementation of OpenSocial needs work - I'd look at other ways if you can... I ended up using the php API.