Corresponding SPDX license identifiers in the source code:

Apache-2.0                Apache-2-license.txt      https://spdx.org/licenses/Apache-2.0.html
BSD-2-Clause                                        https://spdx.org/licenses/BSD-2-Clause.html
BSD-3-Clause              BSD-3-Clause-license.txt  https://spdx.org/licenses/BSD-3-Clause.html
GPL-2.0-or-later          GPL-license.txt           https://spdx.org/licenses/GPL-2.0-or-later.html
MIT                                                 https://spdx.org/licenses/MIT.html
Zlib                                                https://spdx.org/licenses/Zlib.html