SN(1987) neural network simulator for AmigaOS (Leon Bottou, Yann LeCun)
   |
  SN1(1988) ported to SunOS. added shared-weight neural nets and graphics (LeCun)
   |   \ 
   |   SN1.3(1989) commercial version for Unix (Neuristique)
   |   /
  SN2(1990) new lisp interpreter and graphic functions (Bottou)
     |   \ 
     |   SN2.2(1991) commercial version (Neuristique)
     |    |
     |   SN2.5(1991) ogre GUI toolkit (Neuristique)
     |   / \ 
      \ /  SN2.8(1993+) enhanced version (Neuristique)
       |     \ 
       |   TL3(1993+) lisp interpreter for Unix and Win32 (Neuristique)
       |      [GPL]
       |        \_______________________________________________
       |                                                        |
     SN27ATT(1991) custom AT&T version                          |
       |        (LeCun, Bottou, Simard, AT&T Labs)              |
       |                                                        |
     SN3(1992) IDX matrix engine, Lisp->C compiler/loader and   |
       |       gradient-based learning library                  |
       |       (Bottou, LeCun, AT&T)                            |
       |                                                        |
     SN3.1(1995) redesigned compiler, added OpenGL and SGI VL   |
       |         support (Bottou, LeCun, Simard, AT&T Labs)     |
       |                                                        |
     SN3.2(2000) hardened/cleanup SN3.x code,                   |
       |         added SDL support (LeCun)                      |
       | _______________________________________________________|
       |/
       |
     ATTLUSH(2001) merging of TL3 interpreter + SN3.2 compiler
     [GPL]         and libraries (Bottou, LeCun, AT&T Labs).
       |
     LUSH(2002) rewrote the compiler/loader (Bottou, NEC Research Institute)
     [GPL]
       |
     LUSH(2002) rewrote library, documentation, and interfaced packages
     [GPL]      (LeCun, Huang-Fu, NEC)

I love this diagram. Is there a tool that generates such things? Or is there a name for this style of diagram that I could search for?

My prime use would be generating diagrams of function call chains in large Python code bases.

Where does Ralf Juengling's work on lush fit in to this picture?