Elgg is an open, flexible social networking engine, designed to run at the heart of any socially-aware application. Building on Elgg is easy, and because the engine handles common web application and social functionality for you, you can concentrate on developing your idea.
Elgg is open source. That means, when you use Elgg, you have the benefit of being part of a large developer community, with the security and stability that hundreds of eyes can provide. It’s also headed and used by Curverider and its partners, so you can be assured that it’s in commercial use and will cope with the demands of a popular application.