bits.netbeans.org is a virtual host in netbeans-vm.apache.org
This virtual host is configured using puppet with this YAML file https://github.com/apache/infrastructure-puppet/blob/deployment/data/nodes/netbeans-vm.apache.org.yaml
Let's Encrypt Certificates
Let's Encrypt certificates are a chain of certificates that include netbeans-vm.apache.org and bits.netbeans.org. Firefox will complain about this chain, but Chrome won't.
Certificates will be automatically renewed.