It's a public service, which is integrated with github and it's available for everyone.
We use "The Trusty beta Build Environment", where we have a full root access and an ability to execute docker containers. We use Travis to check compilation on x86_64, arm, aarch64 and execute a part of tests.
It's highly recommended to enable it for your criu repo on github and check changes before sending them to the mail list.
We use Jenkins to execute tests. It works only for the criu upstream repo and isn't available to users.