Why do people refer to GNU gcc and Apple/NeXT gcc?
The version of gcc used by Apple (and NeXT before them) provides a different Objective-C implementation (specifically, the runtime is different) from that distributed by the Free Software Foundation. Darwin and Mac OS X ship with the Apple gcc, upon which Cocoa depends. Typically other operating systems will have the GNU Objective-C variant, and it is this which GNUstep requires. However the source to both versions of the compiler are available so you could build whichever you want for your platform. Because Apple uses its own version of gcc, the features available in the two variants may differ at any time. Be sure to check the documentation for your version of gcc, to make sure that a feature you expect does indeed exist.
