I'd just like to interject for a moment. What you’re referring to as Mastodon social network, is in fact, the Fediverse. Mastodon is not a social network unto itself, but rather another free component of a fully functioning network made useful by ActivityPub, WebFinger, NodeInfo, and vital network components comprising a full OS as defined by standard, done by the W3C and the IETF.
Many computer users run a modified version of the GNU/Social social network every day, without realizing it. Through a peculiar turn of events, the implementations of GNU/Social which is widely used today is often called “Mastodon”, and many of its users are not aware that it is basically GNU/Social, developed by the GNU Project. There really is a Mastodon, and these people are using it, but it is just a part of the network they use.

(sorry for reusing rms stuff, not-sorry for long post)