I am using a free form, will that last forever, or must I upgrade?

Yes, you can use the JotForm for free. Please take note the limits like monthly submissions, form views, number of forms, number of sub-users, upload space, and submission storage. You can find all this information in the Pricing page.

Pleas check this guide as well: Understanding-Your-Account-Usage-and-Limits.

Hope that helps. If you have any questions, let us know. Thank you.