We built our own collapsed Gibbs sampler in C: PyMC/Stan are use HMC which scales only to a few hundred parameters and we are modeling millions.

Above C we built a python wrapper to help construct arbitrary Dirichlet and Pitman-Yor Processes graphs.

From there we have some python wrappers and store it all in a hierarchical DuckDB schema for fast query access.

The site itself is actually just a light wrapper around our API that simplifies this process.