Update Dec 25, 2009: If you want to make modifications at source level, then you need Borland C++ 3.1, an old DOS compiler.
Finally, I found it! Is a CNC software from Yeager Automation under DOS system. Is written in C language (exactly, Borland C) and can drive a 4 axis router. CNC stands for Computer Numerical Control, my strongest hobby :p . What is so special with it? Well, is not the best CNC software under DOS operating system (in my opinion, TurboCNC is the one) but Yeager put it in Public Domain with sources.
Yep, now you can study it and modify it as you like, Where can be found? Here. Is a Yahoo group. Of course, is easy to put it on my site but I respect that comunity. So, if you want it, you must have a Yahoo email acount to join. There you will find also tweaked variants from members in File section.
If you want more details about this CNC thing, here you can find a very nice and detailed walk-through.
CNCPro main screen under Dosbox DOS Emulator. Of course, I can't use it under an emulator and on a MAC computer without paralel port but I did it to see how it looks. Also, I did a compilation test under the same emulator with Borland C++ 3.1 . Zero compilation errors :p .
Borland C++ 3.1 and a successful compilation of CNCPro. Turbo Vision is the best text user interface in the world. I tested the generated code and is perfectly valid, works well on a PC.
CNCPro in his natural environment at Yeager Automation.
Some said about the code that is hard to "decode". I'm curious...