GNU emacs has been in continuous production for something like 35 years, and it's somewhat difficult to imagine it ever going away.
Is there an older piece of software that we still routinely use?
Is there an older piece of software that we still routinely use?
https://en.wikipedia.org/wiki/TeX
which is underlying the LaTeX set of macros and stuff that is still in use for academic papers.
[edit] Also TeX is a good example to bring up as an early example of a complex system that was intended to have freely available source code (before the term "open source" and before GNU).
When he created TeX, Knuth said there was a lack of example source code that could be freely examined by students and others in the field, so he released the code and in fact published it in book form along with the source for Metafont and the code for the Computer Modern fonts.
vi is from 1976 [2]
[0] https://en.wikipedia.org/wiki/BLAS
IBM VM dates back to 1972. IBM's other mainframe operating systems trace their lineage back to OS/360, which is 1966. The XEDIT editor is 1980.
I believe codebases for all of the above are still in active development and are certainly in active use.
Stuff like cat, sed, awk, od, dc, head, vi, echo, sh, uniq, diff, sort, and so on.
I suspect, due to it's widespread use in embedded systems of all sorts, there will be things still running MS-DOS 50 years from now.
Pretty sure SCO Unix (yes, you can still buy it) is System V tar. Probably Solaris, too.
I recall AIX tar is...something else, none of the above. I don't recall the details.
A tar command appeared in Seventh Edition Unix, which was released in January, 1979. There have been numerous other implementations, many of which extended the file format. John Gilmore's pdtar public-domain implementation (circa November, 1987) was quite influential, and formed the basis of GNU tar. GNU tar was included as the standard system tar in FreeBSD beginning with FreeBSD 1.0. This is a complete re-implementation based on the libarchive(3) library. It was first released with FreeBSD 5.4 in May, 2005.