PlatformIO is an open source ecosystem for IoT development with a cross-platform build system, a library manager, and full support for Espressif (ESP8266) development. It works on the following popular host operating systems: macOS, Windows, Linux 32/64, and Linux ARM (like Raspberry Pi, BeagleBone, CubieBoard).

• What is PlatformIO?
• PlatformIO IDE
• PlatformIO Core (command line tool)

ESP8266 core includes an xtensa gcc toolchain, which is also under GPL.

Espressif's NONOS SDK included in this build is under Espressif MIT License.

ESP8266 core files are licensed under LGPL.

umm_malloc memory management library written by Ralph Hempel is used in this project. It is distributed under the MIT license.

BearSSL library written by Thomas Pornin, built from https://github.com/earlephilhower/bearssl-esp8266, is used in this project. It is distributed under the MIT License.

LittleFS library written by ARM Limited and released under the BSD 3-clause license.

uzlib library written and (c) 2014-2018 Paul Sokolovsky, licensed under the ZLib license (https://www.zlib.net/zlib_license.html). uzlib is based on: tinf library by Joergen Ibsen (Deflate decompression); Deflate Static Huffman tree routines by Simon Tatham; LZ77 compressor by Paul Sokolovsky; with library integrated and maintained by Paul Sokolovsky.