From what i saw in the source code, it's a feature that lets sqlite open a database file stored on a web server. There is a class in the code HTTPVFS [1] that proxies sqlite's filesystem operations to http requests.
I'm the author, yes @niea_11's comment is right. We add a HTTP Virtual File System. So you can stream the SQLite files over a static HTTP Server like Amazon S3 using HTTP Range Headers to do it efficiently. No dynamic web software needed.
[1]:https://github.com/plasticityai/supersqlite/blob/01e54bbb829...