The ROMs of ESP32 series of chips are Copyright (c) 2015-2022 Espressif Systems (Shanghai) Co. Ltd.
The ROMs also include various third-party libraries. The list along with the respective licenses is available here.
The ROM code of the currently available ESP32 series of chips is not open-source.
The ROM binaries are released under the Apache License Version 2.0, as noted here.
17-02-2024
cc merel