TN kernel with C++ wrappers and set of drivers for NXP Cortex-M MCUs also in C++.
The author of RTOS TNKernel is Yuri Tiomkin. Github repo is https://github.com/yuri-tnk/TNKernel_v3. It is distributed by BSD-3-Clause license. This code doesn't contain most of TNKernel code base. The main reason for this repo is to introduce C++ wrappers for it.
The author of these wrappers is Andrey Serdtsev. I worked with him on the implementation of some parts of it.