I remember somebody pointing this out a while ago, and i think the devs said they dont plan to release it, and it was just an experiment to test the possibilities of the game engine.
Nah, there's no hidden wheels in there. Also that was more like a physics experiment, to show that you can do pretty much what you want in BeamNG. Weird crawling creatures? No problem.
I made it in 2014. Seems like I've lost it, it's not even in my backups. It was broken last time I tried it, as some new torque effect kept twisting the body. It is basically a flexible spine with a single rotator in the head, connected to cranks in each segment. Beams from the cranks move the legs. Each pair of legs is a quarter phase ahead, which is where the wavy crawling movement comes from. Steering hydros bend the body sideways. Now I'd probably use hydros to move the legs directly and lua to control them.
Start with small and improve from that to something that can actually move. https://wiki.beamng.com/JBeam_Introduction You can start also with something really simple like this (don't steal my sword model): It really does not do much of anything, but making something such simple gets one started in learning how jbeam really works. Using blender to make edges (beams) and nodes (vertexes) is quite simple and there is no need to worry about graphics. Really simple to make, add triangle shape, remove faces, add two edges for cross bracing the shape, then just export as jbeam: https://wiki.beamng.com/Blender_Exporter_plugin Then you can add to shape whatever you want, experiment. Look beginner Blender tutorials from YT if you don't know how to use Blender.