It's structured as a multi-stakeholder cooperative, from what I understand.

"Building an artist-owned platform is a complex challenge, but it’s one we are uniquely positioned to solve. Our growing coalition includes founders of Ampled, a project that helped pioneer the concept of cooperative platforms, as well as artists, music industry professionals, and specialists in cooperative law and platform economics. "

From a introductory blog post.

https://subvert.fm/blog/a-collectively-owned-bandcamp-succes...

More on the co-op model in the FAQ.

https://subvert.fm/docs/what-does-it-mean-to-join-the-co-op/