These days yes. Has LLVM and GCC front ends too, very easy to get going with it.
D wasn't Boost licensed when I looked at it as a replacement for C++ about a decade ago. Wiki thinks the backend has been available since 2017. It looks like the source may have been available for longer than that but I missed the distinction between source available and open source if it was. That's how I ended up on the C++ path instead of the D one anyway, seems a credible risk others have the same experience.
The front end was open sourced around 2005 or so, and it was also paired with gcc to have a fully open sourced Gnu D gdc compiler. There's also the fully open sourced ldc compile based on LLVM.
We couldn't get the dmd backend open sourced until 2017, but everything else was open sourced.
