Some plans don’t allow you to share your extensions with others. It’s only meant for testing our product. Cannot share means that only the user who's logged in to miniExtensions (you) can access the extension page. Anyone else will see a notice message.
When you upgrade your plan, your form or portal can be “published” and shared with others. Your end users would not need a miniExtensions (or Airtable) account.
Once you upgrade your subscription, the extension URL becomes "sharable". It can be emailed or embedded on a website for example.