Stallman hasn't been relevant to GCC in 10-15 years. If people aren't doing research projects with it, it's because they don't like the code style (which is still weird but not monolithic) or their funders aren't using it in production.
> This code is licensed under a BSD-like license [8], and LLVM itself will not initially be assigned to the FSF. If people are seriously in favor of LLVM being a long-term part of GCC, I personally believe that the LLVM community would agree to assign the copyright of LLVM itself to the FSF and we can work through these details.
The leads of the project offered LLVM to the FSF and the offer was ignored because of Stallman's incompetent approach to email.
The licence doesn't help but most of this work is open source anyway