> Bot does it mean that if I took Linux Kernel code and stripped all > the comments (which I assume wouldn't have even a tiniest bit of > influence on the functionality) that I would violate GPL?
The only comments you may not remove from the sources are the ones that include the copyright information, since you're not permitted to remove the copyright information. If you wish to remove the comments, and use the result as your preferred means of editing the sources, the GPL won't stop you. What it does prevent is stripping the comments for *only* the distributed sources, as that means that the "sources" you are distributing are not the "preferred form" (obviously, you prefer the form with comments ;). I don't think this info helps with CAD files, though. > Another question: where does the borderline between minimum doc > required from the GPL and additional optional doc lie? Or how can I > determine it? The GPL does not require you to write documentation. The GPL is only concerned with people being able to take your existing sources, modify them, and rebuild the end result. To meet this goal, the *sources* must be reasonably editable. Ancillary documentation is not required, unless of course *you* (the developer) also need such documentation to edit your sources (in which case, you've chosen your source form poorly ;). That part of the GPL is designed to prevent this kind of scenario: A developer has a set of sources, runs it through a preprocessor, and then runs it through a filter which replaces meaningful names like "schematic_flags" with machine generated meaningless names like "var0567_b" in order to effectively prevent people from modifying the code (by making it too difficult to be practical). It also prevents the developer from using a higher-level language (like the FSF's "cgen") to machine-generate a C source file, then distribute only the machine-generated C source file. Documentation is normally licensed as a separate entity, either with the GPL or the FDL.
