No, you do not.
To get started, all you need is the main UpStream plugin from WordPress.org. That plugin provides key project management features and can be used with no extensions.
The UpStream extensions provide extra features, but are not essential:
- Calendar View is needed only if you want a calendar display of Tasks and Bugs.
- Custom Fields is needed only if you need extra information on Projects, Tasks, and Bugs.
- Copy Project is needed only if you need to create one project and duplicate it often.
- Customizer is needed only if you want to change the design of your project’s frontend layout.
- Email Notifications is needed only if you want to send reminders to users about due dates.
- Frontend Edit is needed only if you want to edit projects via the frontend of your site.
- Project Timeline is needed only if you want a Gantt chart for your projects.