The "pillow-heif" source code is licensed under the BSD-3-Clause license, see LICENSE.txt.
License for "pillow-heif" binary wheels: GPLv2, due to base library licenses.

Binary wheels combine several license-compatible libraries. Here they are listed.

Name: libheif
License: LGPLv3
Files: libheif.[dylib|so|dll]
  For details, see https://github.com/strukturag/libheif/tree/v1.23.2/COPYING
  Source code: https://github.com/strukturag/libheif/tree/v1.23.2

Name: libde265
License: LGPLv3
Files: libde265.[dylib|so|dll]
  For details, see https://github.com/strukturag/libde265/tree/v1.1.1/COPYING
  Source code: https://github.com/strukturag/libde265/tree/v1.1.1

Name: x265
License: GPLv2
Files: libx265.[dylib|so|dll]
  For details, see https://bitbucket.org/multicoreware/x265_git/src/4.2/COPYING
  Source code: https://bitbucket.org/multicoreware/x265_git/src/4.2

Name: MinGW-w64 runtime (Windows wheels only)
License: GPL-3.0-with-GCC-exception (libgcc, libstdc++), MIT and BSD (libwinpthread)
Files: libgcc_s_seh-1.dll, libstdc++-6.dll, libwinpthread-1.dll
  For details, see https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/COPYING