Torsten: The frame has changed a bit since the photo was taken. If I wanted to start over completely, I'd do it a little differently, but the way I'm going right now doesn't seem too bad. Once I actually start cutting with the router, I may change my mind.
Pythagoras: Yes, the RoboFac software uses the Pythagorean Theorem to calculate the lengths of the actuators. You can download the source code at
http://robofac.sourceforge.net/
and take a look at the file HexapodGeometry.java.
G-code will be generated through standard CAM programs or manually.
If by "drive", you're talking about the motor drives, they're Xylotex stepper drivers. They're located inside the red box that you see on the table in the photo.
Linux, to me, is no great effort. Of course, the RoboFac software runs on Windows (and maybe even Macintosh) now, it just doesn't talk to the parallel port. Perhaps one day the code for driving the parallel port on Windows will get written.
Hexapods have a variety of advantages, including being able to move on 6 axes. After Christmas, I'll post more details.