Thanks for the comments, perceval.
Are your cosmetic suggestions intended for the study interface? Or the browse page?
I've considered trying to make a link swap arrangement with josekipedia, but I've been busy with other things and haven't pursued it.
The new data I'm working on should be much more authoritative than the data I have at the moment. One thing I eventually want to have is a rating by difficulty. I'm not sure whether it'll be best to crowdsource that or come up with some simple rules. Or maybe I could get my hands on some kgs games of various levels and scan them with my tool to see what "joseki" are popular at what levels.
What I'm doing right now:

- Screenshot-System Monitor.png (87.7 KiB) Viewed 8734 times
That's my tree building program using more than 6 cores and 3gb of ram. The GoGoD database has only 68k games, but when you consider rotations et cetera, it's something like 350 million positions I have to examine to build the tree. It was a bit of a trick just getting this to run. It will use about 120gb of hard drive space while it's working.
But I'm not building the whole thing right now, I'm building part of it to test with. Ah, ok, it's done...