There are many kinds of server types on the Fediverse (though Mastodon is by far the most popular right now).
For example, you can follow video livestreams such as @rstv which streams at https://live.retrostrange.com
Or you could follow a video account at @chriswere whose videos are hosted at https://share.tube/a/chriswere/videos
Although they appear to be Mastodon accounts when you interact with them within Mastodon, when you look at them on their home server they're clearly on a totally different platform.
GNU social JP is a social network, courtesy of GNU social JP管理人. It runs on GNU social, version 2.0.2-dev, available under the GNU Affero General Public License.
All GNU social JP content and data are available under the Creative Commons Attribution 3.0 license.