Can I add an additional editor on the form?

I have a form that I'd like to share with another user for him to continue editing and developing.  How might I go about doing this?

Adding their account as a sub-user and giving them access to that form will allow for them to edit it without having to give them access to your account:

https://www.jotform.com/help/232-How-to-share-forms-with-a-sub-account-user