I have started to play with OpenPNE, a php based open source SNS. The license is GPL2.0.
Well, I am thinking of integrating it with ISSO.
Current problem is that the development documentation is so thin, that it is kind of difficult to find out the starting point. I have been doing it for a couple of weeks and finally I am starting to see the file structure.
Anyhow, I will keep posting on the progress.