1Eigen is primarily MPL2 licensed. See COPYING.MPL2 and these links:
2  http://www.mozilla.org/MPL/2.0/
3  http://www.mozilla.org/MPL/2.0/FAQ.html
4
5Some files contain third-party code under BSD or LGPL licenses, whence the other
6COPYING.* files here.
7
8All the LGPL code is either LGPL 2.1-only, or LGPL 2.1-or-later.
9For this reason, the COPYING.LGPL file contains the LGPL 2.1 text.
10
11If you want to guarantee that the Eigen code that you are #including is licensed
12under the MPL2 and possibly more permissive licenses (like BSD), #define this
13preprocessor symbol:
14  EIGEN_MPL2_ONLY
15For example, with most compilers, you could add this to your project CXXFLAGS:
16  -DEIGEN_MPL2_ONLY
17This will cause a compilation error to be generated if you #include any code that is
18LGPL licensed.
19