“As soon as this innocent little OS turned 21 in 2019, Microsoft grabbed it, acquiring ThreadX owners Express Logic and rebranding the poor thing as Azure RTOS, which hasn’t done any favours for its brand awareness.”
Microsoft claims 12 billion devices run ThreadX, including the firmware on every Raspberry Pi bigger than the Pico. It bought the RTOS soon after AWS took over FreeRTOS, renamed it after a cloud product, and now hands it to the Eclipse Foundation under MIT. Four years of Azure branding did nothing for it. Microsoft is giving away what it could not sell.