You see, I originally thought that all code built on (or built for) something was derivative code - but that is not true. For example, apple uses Linux parts in their OS - yet their OS isn't released under the GPL.
If you're referring to gcc and the bash shell, these are not a part of Linux. These are independent programs, and Apple's use of them is subject to the GPL. For instance, if Apple makes modifications to gcc, these modifications must be licensed under the GPL.
If Apple was to borrow parts of the linux kernel into their own kernel for instance, then they'd have to release their own kernel under GPL.
