Original Authors:
Davy Temperley: http://theory.esm.rochester.edu/temperley/
Daniel Sleator: http://www.cs.cmu.edu/~sleator/
John Lafferty: http://www.cs.cmu.edu/~lafferty/

Much additional work has been done by many different developers.
The current lead developer is 
Linas Vepstas: http://linas.org/

Some of the people who have contributed patches and fixes include:
(In alphabetical order)

Borislav Iordanov <borislav.iordanov_at_gmail.com>
Dom Lachowicz <domlachowicz_at_gmail.com>
Marc Maurer <uwog_at_uwog.net>
Evgenii Philippov <efilippov_at_gmail.com>
Sampo Pyysalo <smp_at_is.s.u-tokyo.ac.jp>
Murilo Saraiva de Queiroz <muriloq_at_gmail.com>
Fridrich Strba <fridrich.strba_at_bluewin.ch>
Peter Szolovits
Vikas N Kumar <walburn_at_gmail.com>