SSL is provided. This isn't a typical CDN. This is a way for people who don't want to setup a CDN or deal with the cost to upload their files and receive the markup to use on their site. So custom domains wouldn't be a feature we'd offer in the near future, but always something to consider.
This is an easier approach for getting content onto a CDN. All you have to do is upload the files to the dashboard, and you are ready to go. The system provides you the markup to put in your code to use the css or js file.
AirCSS can be used alongside Cloudflare, but if someone wants an easy to use CDN that isn't limited to using Cloudflare DNS (like if they want to use nsone or another DNS provider), they can use AirCSS to easily get their files on a CDN.