Thanks. That helps me provide better information.
I can only describe the law -- because something specific to the way the interface works would require the kind of extensive analysis that only one's own lawyer could provide (it is just not an easy answer without analysis and technical understanding).
With that caveat, the law is like this:
Software that cracks or cuts through protections built into a database's protective software would pose a potential to violate copyright law. Here's a link to one key section of this law on "anti-circumvention." http://www.law.cornell.edu/uscode/text/17/1201
It may be useful, also, to read about the administrative rules that augment the law. These are made by the Librarian of Congress, who is the administrative law giver for copyright. There are several rulemakings that you can access from this site:
But there is less chance that a copyright violation would occur if the technology merely enhanced the ability of someone who is a legitimate user of a database program to read the data (without cracking any codes or circumventing anti-piracy protections). This is analogous to someone using a voice generating software package to read aloud data that is normally displayed on-screen.
So really, the key issue is how the two software programs interact -- and how the one that makes the underlying program more user-friendly achieves its goals.
This is not to say that, even if something was more like a voice generator than a digital crowbar, the copyright holder for the database would not be aggressive, even overly-aggressive in trying to shut down access by the overlay software. Sometimes, there are business decisions that go that way -- and it can take money and time to then conduct a legal fight.
Please let me know if any of this information requires clarification.
I wish you every success with your venture!