Gedalia Pasternak is the stupid bloke who designed Expression in the first place and runs this site
Janak Parekh was one of the other founders of Altiverse. He has helped with the original brain storming behind Expression, he's done quite a bit of work helping me get the project off the ground including site design, figuring out winCVS and ssh.
Holister Herhold is current working on getting the Expression Linux port up and running (he's responsible for all the #if def GCC in the code)
Ryan Villamil helped me with the annoying math behind getting a skeletal system into local space and attaching other objects to it in real-time.
Fred Park and Keith Waters published the original linear muscle model based on a cosine fall off function