There is no official XScreenSaver GitHub repository.

I am jwz, the author of XScreenSaver, and I do not publish a public source code repository. I publish releases as tar files on the official web site and only there. If you see any other XScreenSaver repository (on GitHub or elsewhere) that has nothing to do with me and you should not trust it.

I welcome submissions and change requests via email. It's fine. You'll get over it.