Many people have contributed to lmfit.

Matthew Newville wrote the original implementation.
Till Stensitzki wrote the improved estimates of confidence intervals,  and
     contributed many tests, bug fixes, and documentation.
Daniel B. Allan wrote much of the high level Model code, and many
     improvements to the testing and documentation.
Antonino Ingargiola wrote much of the high level Model code and
     provided many bug fixes.
J. J. Helmus wrote the MINUT bounds for leastsq, originally in
     leastsqbounds.py, and ported to lmfit.
E. O. Le Bigot wrote the uncertainties package, a version of which is
     used is lmfit.

Additional patches, bug fixes, and suggestions have come from
  Christohp Deil, Francois Boulogne, Colin Brosseau, nmearl,
  Gustavo Pasquevich, LiCode, and Ben Gamari
