I dont think I've ever seen a commit that says "49 years ago". Damn.
Not quite as old, but brl-cad is still in active development and has commits from 1983. https://github.com/BRL-CAD/brlcad/graphs/contributors?all=1
1968 https://www.netlib.org/go/fft.f
https://github.com/dspinellis/unix-history-repo
alt Hacker News
Not quite as old, but brl-cad is still in active development and has commits from 1983. https://github.com/BRL-CAD/brlcad/graphs/contributors?all=1