The ROOT system is being made available under the LGPL 2.1 or (at your option) any later version, which allows ROOT to be used in a wide range of open and closed environments. The LGPL is copied verbatim below.
The optional MathMore library uses the GSL library which is licensed under the
GPL and hence the MathMore library is only available under
the GPL (to exclude MathMore from ROOT run configure with the
RooFit is distributed under a University of California and Stanford University license.
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