1.  .\Middlewares\FreeRTOS\FreeRTOS_v202012.00
FreeRTOS is freely available under a MIT license.The source code is derived from "https://freertos.org/".

2.  .\Middlewares\RealThread\rtthread-nano-master.zip
RT-Thread is freely available under a Apache License 2.0.The source code is derived from "https://www.rt-thread.org/download.html#download-rt-thread-nano".

3.  .\Middlewares\RTX5\CMSIS_5-develop.zip
Keil RTX5 is an open-source, deterministic real-time operating system implementing the CMSIS-RTOS v2 API, a generic RTOS interface for Cortex-M processor-based devices.The website is"https://github.com/ARM-software/CMSIS_5"