Maxima (http://maxima.sourceforge.net/), one of the packages used by Sage, is a quite capable computer algebra system (written in Lisp) with a very long history. It's descended from Macsyma, which was created at MIT in the 1960s. If you look through some of the Maxima source files you'll find modification dates from the '70s. That has to make it one of the oldest still-active software projects. Heck, it's older than Unix!
The relationship of Sage with existing open source projects was something I never quite understood. Instead of investing their knowledge and time into improving the capabilities of existing systems (SciPy, NumPy or Maxima, Octave) to bring them up to par with the more pervasive commercial offerings (Matlab, Mathematica, Maple), they basically just bolted Python onto everything without in the end improving anything. Sage to me always seemed as just some kind of Python promotion vehicle trying to hide the fact that basically all the underlying systems it uses are written in other languages.
