I *think* it could be PHP, but it's hard to tell. They have query delimiters (ie: "?"), but the site also has a nice "Wordpressy" feel to it don't you think? : ) Now, to answer your question in your subject line... my suggestion is to hire a programmer at ODesk, Elance, or VWorker (formerly RentACoder). Of course, if you have the time... then go for it and build it yourself. Best, - Jay
By looking at the response headers it appears to be running on Linux servers using Ruby. Given there are social networks written in C++, Ruby, .Net & Java with databases in MS SQL, MySQL & Oracle, you can basically write them in any serverside language.