We present a free and open source firmware designed to operate as an Intelligent Platform Management Controller (IPMC). OpenIPMC is based on the FreeRTOS real-time operating system and is designed to be architecture-independent, allowing it to be run on a variety of different architectures. It has been tested successfully on Zynq Ultrascale+ (ARMv7-R) and ESP32 (Tensilica Xtensa LX6) devices. Having a fully free and open source code is an innovative aspect for this kind of firmware, allowing full customization by the user. This work aims to describe its development, features and usage.