NextCloud is NextCloud. No one owns them. They publish their code on github, and you can find their license here:
🌏 Our website. Contribute to nextcloud/nextcloud.com development by creating an account on GitHub.
github.com
I use NextCloud, and I plan on using them in future. Cheaper and way better solution than anything apple/google/ms can offer. At least for my use case scenario. And if you know how to set it up for your own needs, NC is brilliant!
I'm also glad that they are growing rapidly. They are turning profit since 2016., and it's nice to see that a project like this one can succeed.