Realtime SMP Kernel, networking, file-systems, drivers, BSPs, samples, and testsuite.
musl - an implementation of the standard library for Linux-based systems.
FatFs is a generic FAT/exFAT filesystem module for small embedded systems. The FatFs module is written in compliance with ANSI C (C89) and completely separated from the disk I/O layer.
FreeRTOS kernel files only, submoduled into https://github.com/FreeRTOS/FreeRTOS and various other repos.