Has there been a concentrated effort to move FreeBSD off of GNU tools (your question seems to imply this)? If so, I'm curious, why? Licensing issues? Architectural issues? Something else?
The first reason probably applies most to big projects like gcc, where it's alleged that the FSF's development process has led to un-modular, hard-to-maintain software. But there are some differences on smaller projects as well, where the BSDs have a tendency to prefer more use of libraries with command-line apps as front-ends to the libs, while the FSF prefers self-contained command-line utilities that interact in the traditional Unix piping style. E.g. GNU tar and GNU gzip are mostly self-contained utilities, while the BSD versions have all the real code in libarchive and zlib, with some command-line frontends.
Some of the more minor rewrites I assume are due to licensing or personality/political issues (I doubt technical reasons are what lay behind OpenBSD writing GNU bc/dc workalikes).
I disagree. Having just spent a week at BSDCan and the attached FreeBSD developer summit, I'd say that the biggest reason is code quality.
Apple very definitely supported LLVM/Clang because they wanted to avoid GPLv3. FreeBSD is very happy to have a superior compiler available, and the fact that it's BSD licensed is extra icing on the cake. But if LLVM wasn't happening, I'm 100% certain that we would end up importing a newer (GPLv3) version of gcc.