DUCC0 (https://gitlab.mpcdf.mpg.de/mtr/ducc), vendored in rocket_fft/ducc0/, is
dual-licensed under BSD-3-Clause OR GPL-2.0-or-later. Rocket-FFT uses it under
the terms of the BSD-3-Clause license, reproduced below.

Copyright (C) 2010-2026 Max-Planck-Society
Copyright (C) 2019-2023 Peter Bell
Copyright (C) 2026 Philipp Arras

For the odd-sized DCT-IV transforms (derived from FFTW3 and released under the
3-clause BSD license with friendly permission of Matteo Frigo and Steven G. Johnson):
Copyright (C) 2003, 2007-14 Matteo Frigo
Copyright (C) 2003, 2007-14 Massachusetts Institute of Technology

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