Oh well, you can still have some fun riding it like you would a mini bike on private property or in another off Road area that its allowed to ride in.
looking again at the project, if the engine was placed just a little higher and maybe just slightly forward, you could have a set of cranks with very small sprocket, that would function just enough to make it legal, I've thought about building a frame up similar to what you've done here myself and might get it done one of these days.
So many projects in my head and so little time to attempt them...LOL!