Rivet was initially developed as one of several tools in the CEDAR collaboration (we also produced HepForge?, HepData, and AGILe), and has since been extended by a multitude of people, mainly connected to the MCnet EU training network: authors of the Professor MC tuning system, and the Sherpa and Herwig++ event generators have been particularly active.
The lead developer is Andy Buckley. Other active developers are Chris Pollard, David Grellscheid, Frank Siegert, and Holger Schulz. Contributions have also been made by Hendrik Hoeth, James Monk, Eike von Seggern, Emily Nurse, Lars Sonnenschein, Gavin Hesketh, Jon Butterworth, Leif Lonnblad, Ben Waugh, David Voong, Mike Whalley Matthew Wing... and more that I'm forgetting!
If you want to join in, please contact us! We are very keen to get more analyses into our framework, particularly from the LHC, HERA, the B-factories + CLEO, and older experiments (such as SLD, ISR, JADE, UA5...). Your assistance --- particularly if you know the experiment/analysis first-hand --- would be very welcome.