I kind of started this with a less than serious comment about Misant's OpenRail-based design not being exactly a ShapeOko. One of Edward Ford's stated goals was "one standard design" (and later down that page
he says there are "documented upgrades"). As far as the BOM goes, Misant's design
has only the dual bearing V-wheels and the smooth idlers in common with the ShapeOko (besides some standard fasteners, of course -- and possibly the belts, although not the pulleys). It uses the same V-wheel-on-V-rail principle, but so do numerous other CNC machines; same can be said about the arrangement of the axes. I'm sure it started as a ShapeOko and went through a series of small changes, each stage not so different from the previous one as to merit a new name, but the sketch we saw, without the intermediate steps, looks very different from a ShapeOko.
Now, what makes a ShapeOko a ShapeOko? I think not one of the characteristics is strictly necessary. For instance, if I take a bog-standard ShapeOko and replace the Makerslide with 20x40 extrusion and OpenRail, that's still a ShapeOko. If I replace the MXL belts with GT3, that's still a ShapeOko. If I route the belts differently, that's still a ShapeOko. If I replace the belt drive on a standard ShapeOko with an acme leadscrew, that is pushing it. If I move the Y motor(s) on the frame and use closed-loop belts, but I keep the standard motor plates, that's somewhere in between. If I add another length of Makerslide on the X and modify the carriage, that's still a ShapeOko.
When is it no longer an "upgrade" but a different machine entirely? That's a bit like Nasreddin Hodja's 9000-year-old knife. When the blade became too worn, the current owner replaced the blade. When the handle became too worn, they replaced the handle. So it's the same old knife, only "upgraded" a lot. Same here: I'm sure you can start with a ShapeOko and upgrade it bit by bit until it's a $1m industrial six-axis CNC milling machine the size of a bus. At some point, you'll have to stop calling it a ShapeOko, but I don't think it's terribly important when that happens -- nor is it terribly important that we agree on that moment, even. So I wonder why I even bothered to waste so many electrons talking about this... but then again, when is philosophy no longer philosophy and becomes a waste of time?