lmfit is released under the LMFIT-BEER-WARE licence:

In writing this software, I borrowed heavily from the public domain,
especially from work by Burton S. Garbow, Kenneth E. Hillstrom,
Jorge J. Moré, Steve Moshier, and the authors of lapack. To avoid
unneccessary complications, I put my additions and amendments also
into the public domain. Please retain this notice. Otherwise feel
free to do whatever you want with this stuff. If we meet some day,
and you think this work is worth it, you can buy me a beer in return.

- Joachim Wuttke <j.wuttke@fz-juelich.de>
