In the licence text is written: "As a special exception, the copyright holders of FreeRTOS give you permission to link FreeRTOS with independent modules to produce a statically linked executable,..."

My question: Is this exception valid for modified FreeRTOS, too? Or in other words. Does this exception also cover: "As a special exception, the copyright holders of FreeRTOS give you permission to link FreeRTOS or modified FreeRTOS with independent modules to produce a statically linked executable,..."

I know, I have to put the modified RTOS under GPL and have to publish it.

Regards Alex

Assuming you publish the modifications separately (perhaps by uploading to the FreeRTOS Interactive site) then I would say the exception applies to binaries generated by the modified version too.