I assume that the vast majority of the people who created the software for these missions are now retired (the "space pensioners" of the Voyager mission).
Here's a very good summary of the current software team of the Voyager missions
Here's another brief mention of exactly what programming language was used
But in the last 40 years of progressive development, programming languages have advanced a lot. Once, the Voyager team had over 200 employees, now there are 8 (here's a very good audio article about the Voyager Team, here is a summary).
After all, the two probes were programmed with Fortran and Assembler. In the space probes themselves, General Electric's ancient processors do their work. They have to make do with a 64 kilobytes of memory (this interview explains that they are 64 kB, not less as some claim).
FORTRAN TO PYTHON
Interestingly, there is a Fortran wrapper in Python (more info). Is this or a similar solution used by the Voyager team?
It would certainly be a possibility to adapt the aging source accordingly. Whether the Voyager team uses Fortran 77, or C, or wrapper for both, I couldn't see that yet. There the information is simply still too spongy.