Thanks! You're right, the discussion group is no longer very active, but we do get occasional library updates directly from their maintainers. I try to upload them to the Hosted Libraries CDN soon, but sometimes it can take me a few days. Your mails here directly reach my inbox, so please always feel free to ask if something seems missing! I'm happy to help out.
For the stuff we do host, it's served as part of Google's global high-performance static file serving infrastructure, so there's a big team dedicated to keeping the machinery well oiled and serving the files super fast :)