Here is the honest line between free and paid.
The free plugin includes
- Unlimited cloud storage for your own layouts, sections, rows, modules, and snippets.
- Sync of your own library across all your sites.
- Import of your saved items inside the Visual Builder.
A membership adds
- The premium curated library of Divi 5 native sections, layouts, and child themes.
- The Copy button that brings a premium piece into your site.
- The page builder for assembling a full page from library pieces.
- Saving your own global Design Variables and Presets to your account.
Put simply: the plugin is free for your own content. The premium collection is what you pay for. See DiviVault plans.