Zapier's Dropbox integration can only trigger on new files in, and upload files to folders in your Dropbox. Any shared folders you have access to are invisible to Zapier.
We've created a custom Zapier + Dropbox integration that let's you access shared folders in your zaps.
We'll install a private version of the custom Salesforce integration in your account.
You are not getting IP ownership nor licencing the integration from us. We just install a pre-built custom integration in your account. On top of that, Zapier prohibits you from selling access to others.
The integration will automatically be available to use in zaps you build in your account, and you can share access to others via a special invite URL (remember, no reselling!)