Awesome open source projects of the past and what we choose to do with them now

[ChickenLogic]

Since I didn't post a useful thread in quite some time I thought I should do my part to improve this forum with some quality content:

There are a number of awesome open source projects that are 'dead' for a number of years now simply because people don't even know they exist. This thread is dedicated to cool chess algorithms that are forgotten by now and could be very useful if we decide to work on them again.

I'll start with naming one I came across recently: Natch 3.3
It is a retrograde analysis tool for proof games. It was written on a DOS machine but works fine even on modern systems. I bet there are quite a few performance optimizations that are trivial for today's knowledge about algorithms and programming languages. One such thing is of course multi threading.
It can be used to prove that a position is in fact possible to reach from a classical starting position. Further use include to find the fastest possible move sequence to a certain position. This can be very useful if combined with Stockfish evaluation and a threshold to compose 'real life like' chess games for movies or books (if one has a finish in mind like an awesome puzzle). I bet there are other uses for such an algorithm as well.

If you know a 'dead' open source project that deserves some much needed love I'd welcome you to post about it in this thread.