Plugin developers must follow the same licensing terms as WordPress.com.
This means that most plugins are free to use, but there are a few exceptions, such as premium plugins that may require a fee for use.
Some plugins, like security plugins, may require an account with a hosting provider like WP Engine or Siteground. These providers offer free plans that allow for limited plugin use.
Plugin developers must also follow the plugin guidelines set by WordPress.org.
These guidelines include things like being clear about how the plugin works, being responsive to user feedback, and following best practices for code quality.
Overall, plugins can be used on a free WordPress installation with some restrictions. Developers must follow the same licensing terms as WordPress.com, and some plugins may require an account with a hosting provider.
With careful planning, plugin use on a free WordPress installation can be manageable and helpful. In the end, the use of plugins is up to the discretion of the developer.