It's not an error, it's just saying the project exceeds the free edition limits, which means you can look around and preview it but not make edits to it.
So it’s a warning, not an error, but it looks like an error to someone who hasn’t learned how the thing works.
If it were me, I’d make that first click into the demo as simple and clean as possible. The site is currently educating people about a product limitation before they see the actual product.