The OpenTURNS library and all its derivatives are distributed under the LGPL license, see COPYING and COPYING.LESSER.

This library bundles several third-party codes with various licenses compatible with the LGPL:
- COBYLA optimization solver (lib/src/Base/Optim/algocobyla.*) under Expat license, see COPYING.cobyla
- Mersenne twister RNG (lib/src/Base/Stat/dsfmt.*) under BSD license, see COPYING.dsfmt
- Ev3 symbolic library (lib/src/Base/Diff/Ev3/*) under LGPL license, see COPYING.ev3
- ExprTk symbolic parser (lib/src/Base/Func/openturns/exprtk.hpp) under Expat license, see COPYING.exprtk
- Faddeeva function (lib/src/Base/Func/SpecFunc/Faddeeva.*) under Expat license, see COPYING.faddeeva
- Kendall Tau (lib/src/Base/Stat/kendall.c) under BSL license, see COPYING.kendall
- KissFFT (lib/src/Base/Algo/kissfft.hh), under BSD license, see COPYING.kissfft
- KS distribution from Cephes library (lib/src/Uncertainty/Distribution/cephes/*) under BSD license, see COPYING.cephes
- TNC optimization solver (lib/src/Base/Optim/algotnc.*) under Expat license, see COPYING.tnc
- Gauss Legendre quadrature from FastGL library (lib/src/Base/Algo/fastgl*) under BSD license, see COPYING.fastGL
- Rapidcsv parser library (lib/src/Base/Stat/rapidcsv.h) under BSD license, see COPYING.rapidcsv
