Actually, if you developed and distributed a non-GPL compatible plug-in for GCC, the GCC license prevents you from linking to the gcc stdlib without distributin

Actually, if you developed and distributed a non-GPL compatible plug-in for GCC, the GCC license prevents you from linking to the gcc stdlib without distributing built code under the GPL. It's a peculiar exception - and Apple is almost certainly never going to be in violation of it. Still, the point is that Apple's lawyers are terrified that it could somehow taint iOS/OS X/iTunes if someone comes to believe that Apple might be in violation of it. Why take the chance? Clang is a compliant and fast c/c++ compiler at this point, and is mostly clean code (which is more than can be said of gcc).