There's this application I've been writing and re-writing my whole career: I call it "some users design forms, other users fill out forms." It is hard to design the db as anything other than EAV. (You can push more or less of it into JSON columns, but there are tradeoffs.)

I have often wondered about pushing the customizability down a level though, like what the author does here, where each form creates a separate database table. It's too crazy for me, but it's tempting. And I have actually done it before where users' forms automatically generate individual tables in a separate flattened reporting database. It works really well for giving enterprise customers SQL access to an OLAP view of their data, even if I wouldn't use it for my source-of-truth OLTP structure. (Some day I'm going to write a blog post about that.)

Even just for derived reporting tables, you quickly discover all kinds of limits in your database: reserved words, max columns per table, max columns per query, number of foreign keys pointing at a central table, etc. I haven't hit anything fatal though (with Postgres).

Anyway, I'm excited to see that someone actually pulled this off, complete with Django models and migrations, even if it's just for fun.