"Inviter" is a great addition to any social networking site. It uses the Octazen and OpenInviter platforms to father data. The latter isn't hugely reliable notably for large sites (Facebook, Twitter, Myspace), so we only use the Octazen option. This explains my "Value" rating above being lower as not all inviters are operational - this is the fault of Openinviter though, not the developer.

Andrey is very quick to respond to any questions - even helping out with questions unrelated see more to the product. I recommend him and his programming skills for your project.