Is there a FreeRTOS port for the LPC4088 processor and/or LPC4088-32 board from Embedded Artists which can be built with the Rowley Crossworks for ARM toolchain ? The LPC4088 is a Cortex M4 architecture with floating point hardware support.

If there is a port, where can it be found and how stable is it ?

Rowley uses GCC and there is only one FreeRTOS port for Cortex-M4 for GCC that works on all Cortex-M4 chips without fail, so there is no porting to do. Just start with a working project for that chip then add in the FreeRTOS code. You need to use the port layer in FreeRTOS/Source/Portable/GCC/ARM_CM4F for floating point support.