MoodleNet is a network of independent websites for educators all running the same software. It's what's known as a federated social network. While every website is slightly different in terms of content and emphasis, being part of one is being part of the whole.
MoodleNet is Free and Open Source Software (under the AGPL licence) which can federate with other instances of MoodleNet and other compatible ActivityPub servers. You are encouraged to run an instance yourself, to increase the diversity and resiliency of the federated network.