How can I create a data source in Frevvo Rich Forms, so that I can dynamically load drop-downs and other fields with data from my DB?
Since your Rich Form is external to Adeptia, you'll have to expose your database through a Web Service Provider. The process flow would contain the Database Source activity where your data is stored.
Using Frevvo rules, you can then call the web service provider and retrieve the database data in XML or JSON format. This would populate data from the database into the drop-down.
For more info, please refer to the Frevvo documentation
Note: For Rich Forms within Adeptia, you can follow this method