This was a legitimate concern, which helped in the days GCC originated in, and hurt later on. Parsing C and C++ well and doing intermediate code generation and

This was a legitimate concern, which helped in the days GCC originated in, and hurt later on. Parsing C and C++ well and doing intermediate code generation and optimization was the hard part; taking the result and generating code for a target architecture might well have been proprietary for many architectures if it had been allowed to be, in the era when UNIX and other OS vendors were fighting against each other for every scrap of differentiation. And frontends for some languages would have been proprietary, as well. LLVM's extensible architecture was its most critical property; its permissive license is an unfortunate side effect of a rewrite. If GCC had come up with the "GCC Runtime Library Exception" way back in the day, and provided a modular architecture, half the innovation happening around LLVM might have happened around GCC instead. (Might, not "would have"; we can only speculate on what alternate history might have occurred.)