The rest of the thread linked to gets into the intentional lack of modularity in GCC. Lots of open source, not-really-for-profit projects are benefits from LLVM

The rest of the thread linked to gets into the intentional lack of modularity in GCC. Lots of open source, not-really-for-profit projects are benefits from LLVM in general: Julia, Numba (numerical JIT compiler for Python), Xdress (C++ wrapper generator for Python)...probably many others. Even apart from licensing issues (wanting to stay BSD-compatible), they could not have built on top of GCC. LLVM offers pluggability and modularity. You can use whatever you want from the compiler in a very flexible way; use it only to parse C headers, or use it only for code generation at run-time. GCC is the opposite: Modularity and pluggability has been explicitly prevented because GCC maintainers fear that a pluggable and modular GCC would enable people to "take the edge off the GPL". I guess there is no way around this. For instance, if GCC was to merge the gcc-xml fork which allows you to parse C headers and get the syntax tree as XML back, then somebody could "abuse" that to create a proprietary compiler that uses the GCC parsers. (OK, there is some modularity in GCC now, as I remember a student project in Cython that plugged into GCC using command line flags injecting a shared library in order to parse C/C++ headers; I'm not sure exactly what the status quo is. But it's certainly a very different world from LLVM.)