In every state there are specific laws that pertain to what is and what is not a "motor vehicle" for purposes of needing a license to operate the vehicle on a highway. You need to consult with a local criminal defense attorney who can tell you 100% for sure whether you are correct. If you are correct then you can hire that lawyer to attempt to get the charges dropped. If you do not have funds to hire a lawyer then you can appear in court and plead not guilty and discuss the case with the prosecutor and maybe they will dismiss the charges. However, you need to speak to local counsel immediately so you can be 100% sure of where you stand legally before you go to court.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.