I haven't looked at your project yet (I'm in the train right now) but are you directly using the XML, like Didier's application did?
I wanted to switch to using a relational DB because I find XML both performs not very well, and is quite inflexible. Despite what you can do with XSL or whatever, there's no easy way to add data to it other than editing it directly. I admit that it's also a personal preference: I'm just not too fond of working with XML - I find thinking in relational terms easier.
I wrote a perl parser to convert Didier's TEI XML schema into a series of SQL statements, but since Aran (and others from Sindarin.de) have released a more recent data-set, I have switched to using that one instead.
This it not, however, a large application
- its only a small database, and for now does only read. There are plans to allow users to add notes, their own constructions and possibly a submit-option to a centrally managed "central dictionary".
I stopped using Swing in favour of JavaFX because it offers a much better look & feel, and it's possible to deploy it online and as a desktop application.
Anyhow, it's great that someone's interested - regardless of how you'd want to contribute.