BeRTOS

BeRTOS is a real-time operating system designed for embedded systems.
It is distributed under a modified GPL license with a special exception that grants proprietary applications the right to keep their source code closed while maintaining the BeRTOS code itself open.
It has a very modular design, that allows running it on different architectures, ranging from tiny 8-bit microcontrollers like the Atmel AVR up to the 32-bit ARM architecture, and on hosted environments such as Linux and Microsoft Windows. BeRTOS is open source, written in ANSI C, and supported by popular embedded TLS/SSL libraries such as wolfSSL. 
BeRTOS preemptive multitasking kernel implements many IPC primitives like:
In addition to the kernel, BeRTOS provides a hardware abstraction layer that includes large number of peripheral drivers (timer, serial, ADC, motors, LCD display, NTC sensors, keyboard, buzzer, memories), algorithms (hash table, CRC, MD2, entropy pool, RLE), communication protocols and a graphic windowing subsystem for small displays.