RcppTrust is distributed under the GNU General Public License, version 2
(GPL-2), because its BOBYQA/NEWUOA ports and R wrappers derive from the
GPL-2 package 'minqa'. It includes code ported from the following sources,
whose notices are retained below.

trust (src/trust_*, R/trust.R)
  Ported from the R package 'trust' by Charles J. Geyer, distributed under
  the following permissive (X11-style) license:

    COPYRIGHT AND PERMISSION NOTICE

    Copyright (c) 2005 Charles J. Geyer
    Copyright (c) 2026 Matthew Fidler

    All rights reserved.

    Permission is hereby granted, free of charge, to any person obtaining a copy
    of this software and associated documentation files (the "Software"), to deal
    in the Software without restriction, including without limitation the rights
    to use, copy, modify, merge, publish, distribute, and/or sell copies of the
    Software, and to permit persons to whom the Software is furnished to do so,
    provided that the above copyright notice(s) and this permission notice appear
    in all copies of the Software and that both the above copyright notice(s) and
    this permission notice appear in supporting documentation.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS.
    IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS INCLUDED IN THIS NOTICE
    BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT OR CONSEQUENTIAL DAMAGES,
    OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
    WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
    ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

    Except as contained in this notice, the name of a copyright holder shall
    not be used in advertising or otherwise to promote the sale, use or other
    dealings in this Software without prior written authorization of the copyright
    holder.

Steihaug trust region (src/steihaug_core.cpp, inst/include/steihaug_types.h)
  Ported from the Rust crate 'basin' (https://github.com/jolars/basin),
  commit 86cc0d6: solver/trust_region.rs, solver/trust_region/steihaug.rs
  and the executor/convergence machinery. basin is copyright its
  contributors and licensed under either of the Apache License, Version 2.0
  or the MIT license, at your option; used here under the MIT license:

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the
    "Software"), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
    OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

BOBYQA and NEWUOA (src/minqa_*.cpp, R/minqa.R, inst/include/minqa_types.h)
  Ported from M. J. D. Powell's original Fortran 77 BOBYQA (2009) and
  NEWUOA (2004) code, which Powell released without a license. The
  unmodified originals are archived at
    https://github.com/libprima/prima/tree/main/fortran/original/bobyqa
    https://github.com/libprima/prima/tree/main/fortran/original/newuoa
  (see also https://www.zhangzk.net/software.html).

  The C++ is translated from the versions of that Fortran modified and
  distributed in the R package 'minqa' 1.2.8 (copyright Douglas Bates,
  Katharine M. Mullen, John C. Nash, Ravi Varadhan; GPL-2), keeping its
  error-code and printing edits, and R/minqa.R and the print glue in
  src/minqa_common.h follow minqa's R/minqa.R and src/minqa.cpp.

  References:
    M. J. D. Powell (2006), "The NEWUOA software for unconstrained
    optimization without derivatives", in G. Di Pillo and M. Roma (eds),
    Large-Scale Nonlinear Optimization, Springer, 255-297.
    doi:10.1007/0-387-30065-1_16
    M. J. D. Powell (2009), "The BOBYQA algorithm for bound constrained
    optimization without derivatives", Report DAMTP 2009/NA06, Centre for
    Mathematical Sciences, University of Cambridge.
