> A FOSS project can be FOSS and refuse all other contributions.
It can, yes. There's nothing preventing it, except that it's a shitty way to work in the open, and you may as well make the project proprietary or source available. The maintainers might have their own vision of the project direction, and they may reject contributions, but refusing contributions outright is how forks are made. Nothing wrong with that either, but usually the projects that are more receptive and responsive to user feedback are the ones that users and developers gravitate towards.
It can, yes. There's nothing preventing it, except that it's a shitty way to work in the open, and you may as well make the project proprietary or source available. The maintainers might have their own vision of the project direction, and they may reject contributions, but refusing contributions outright is how forks are made. Nothing wrong with that either, but usually the projects that are more receptive and responsive to user feedback are the ones that users and developers gravitate towards.