From https://www.apple.com/legal/sla/docs/macOSBigSur.pdf
"B. Certain software libraries and other third party software included with the Apple Software are free
software and licensed under the terms of the GNU General Public License (GPL) or the GNU Library/
Lesser General Public License (LGPL), as the case may be. You may obtain a complete machinereadable copy of the source code for such free software under the terms of the GPL or LGPL, as the
case may be, without charge except for the cost of media, shipping, and handling, upon written request
to Apple at opensource@apple.com. The GPL/LGPL software is distributed in the hope that it will be
useful, but WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. A copy of the GPL and LGPL is included with the Apple
Software."