I have a question - I've briefly looked at the API, and it seems like a mostly general-purpose user interfance library.
What do you think of replacing the 'render' part with something that's more like a generic UI? You could keep the UX the same, yet your app would look like a desktop app (or at least close to it).
Trying to fit in the limitations of 80x25 text rendering is cool, but there's nothing in the underlying architecture that of modern graphics display that's predisposed to that, it all ends up as GPU commands.
I'm sure you could get most of the way to what I'm describing with just replacing the font/character set with one that renders things like borders in greater detail.
Hell, you could even add this as post-processing. You look at the terminal output with cellular automata like rules, and try to render UI primitives fitting that.