I will use this opportunity to mention Maxima (https://en.wikipedia.org/wiki/Maxima_%28software%29 https://en.wikipedia.org/wiki/Maxima_%28software%29) that was

I will use this opportunity to mention Maxima (https://en.wikipedia.org/wiki/Maxima_%28software%29 https://en.wikipedia.org/wiki/Maxima_%28software%29) that was developed by one of the best math professors that I have had the privilege to learn from: Bill Schelter. It was forked from Macsyma and released under the GPL and still appears to be actively maintained.