Prior to Amazon buying out FreeRTOS (along with its creator and maintainer) and relicensing it to MIT, it was "GPL with exceptions". Clause 1 would be OK if it

Prior to Amazon buying out FreeRTOS (along with its creator and maintainer) and relicensing it to MIT, it was "GPL with exceptions". Clause 1 would be OK if it left it at "through the FreeRTOS API interface", that's a thing that projects have done to define a more practical boundary than "userspace | kernel or core system library" which the GPL uses on traditional operating systems. (There was a GPL java replacement project that used a "classpath exception" for the java standard library.) But the rest is odd and makes one doubt that the GPL can really be modified this way and still be coherent. Clause 1: ... As a special exception, the copyright holder of FreeRTOS gives you permission to link FreeRTOS with independent modules that communicate with FreeRTOS solely through the FreeRTOS API interface, regardless of the license terms of these independent modules, and to copy and distribute the resulting combined work under terms of your choice, provided that ... + The combined work is not itself an RTOS, scheduler, kernel or related product. + The independent modules add significant and primary functionality that is unrelated to multitasking, intertask communication or intertask signalling - and therefore do not merely extend the functionality already present in FreeRTOS. Clause 2: FreeRTOS may not be used for any competitive or comparative purpose, including the publication of any form of run time or compile time metric, without the express permission of Real Time Engineers Ltd. (this is the norm within the industry and is intended to ensure information accuracy).