Yeah I think you're right. It calls that out (in really tiny footer text) that it's leveraging ml-sharp.
It's pretty trivial to get running locally and generating the PLY files. Spark's a pretty good renderer for it after you've generated the gaussian splats.
This is the heavy lifting: https://github.com/apple/ml-sharp
Previous discussion: https://news.ycombinator.com/item?id=46284658