Greetings! Thanks for your interest in the project. Development of FreeRTPS has been paused for a while. Current development efforts are using FastRTPS and RTI Connext.
At some point it would be to resume development of a microcontroller-friendly middleware option, but at the moment we (OSRF) are not spending time on it. Of course, this is all open-source, so if you have time and energy to spend on FreeRTPS, it’s certainly there for the taking. It would need a significant amount of effort, though. Cheers!