Hi @Pierre_S,
I just checked the ticket and it looks like it was unfortunately moved to the 'not prioritized' category 
I wish I had better news, but for now, the best option for sharing a Retool Form for someone will be via sharing access to the DB so that the From builder can create a Form from the DB schema.
I understand this is not what you want to hear as it does not fit your use case of having a JSON file that can be included in a template.
The best work around could be step-by-step instructions on setting up a Retool DB table or creating and hosting a Postgres DB, along with creating the schema. As this is valuable knowledge that user might not know how to do and they could benefit from this information.
Also, if they have a Form with no DB/schema to upload their data to, a sharable Form won't be of much use. As users will have to create the DB table at some point, so it almost makes more sense to work backend(DB) up to frontend(Form) as opposed to the opposite way. As the Form builder will reduce the risk of human error with column names/types matching exactly to the DB schema.