Your comments

I would also like filtering by more than one keyword. I could see restricting results by date range and by author, for example.

Filtering is nice because it hides the items the user doesn't want to see. Correct me if I'm wrong, but to implement filtering based on user inputs into a search box, I'd have to dynamically remove the existing BibBase elements and script tag, and then add a new script tag to my HTML body which is a copy of the original BibBase one except that it includes the filter parameter.  Or perhaps just reload the whole page, writing out the BibBase script tag on page load, and include the user's search parameters in my page URL so I can find them and insert them into the script tag before I add it to the page. Either way, I get a bit nervous when I'm in charge of inserting elements into my page. I would like it better if search was built in to BibBase, like the controls for grouping are.