The FT8 developers have an amazingly strong knowledge of information
theory as well as the many practical considerations of communication
over an RF channel. Feature addition and bug fixing are slow because
the developers don't believe in abstraction, and instead code as if
the only option were a direct carryover of FORTRAN 77 conventions into
C++. There's no longer a public repo but
https://sourceforge.net/p/wsjt/wsjtx/ci/master/tree/mainwind...
is representative of current code.