One of the interesting things about the experience of LLVM and Clang isn't that it's killing off gcc--a decade after this was written, gcc is still the compiler of choice for most Linux distrubtions--but that it's killing off EDG, the C++ frontend that all proprietary C++ compilers used to use. Killing off proprietary software because the open source stuff is so much better is the vision of Stallman, and it's telling that a permissive license has been much more effective than a copyleft license in doing so.