The source code is a bit bizarre, all the code is repeated for each plugin format, and also full of unrolled loops and inline magic numbers. It makes me wonder if it is actually the result of some compile-to-C++ setup, in which case it's not actually the true source code. If not, it looks like a maintenance hell.
There are coding streams on the YouTube and it seems to be all C++.
The GitHub page for those who found it hard to find: