Interesting.
At one tine, Slackware Linux would not recompile binaries unless the program was patched. So there was a time you could find rather old binaries on Slackware, and maybe still on other distros.
I wonder what the oldest unchanged source/program running on Linux or BSD ? My vote goes to cat(1) :)
FreeBSD /bin/cat has lots of recent changes of substance: https://github.com/freebsd/freebsd-src/commits/main/bin/cat/...
Otoh, /usr/bin/true has only minor changes since initial import (1994) https://github.com/freebsd/freebsd-src/commits/main/usr.bin/...
/usr/bin/false is similar
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