[dfragnito]

Decouple the application from the DB. Use a DB as a service that has an HTTP API. The application encrypts/decrypts all data with public/private key pair. The user, your client generates their own key pair.

This is the scenario we are testing out with http://schemafreedb.com/

You do not have the private key so you cannot see the data but you still can offer the data portion as a service. Your client does need to host the application depending on your target client node may be a good choice or if you want to go mainstream go with something like php.

When ever you have update to the code you can provide a diff of the changes.