How does a close source package work? Depending on the language its not super helpful, but a package that is closed source should be possible.

For crates.io: They don't allow closed-source packages. But they're just the free community package index, you're not forced to use them.

You can:

- host a private index

- host the proprietary binaries in a git repo and use a git dependency

- commit the proprietary binaries into your source repo, and use a path dependency