You can install Flarum with the package manager. If you install from the Zip, the package manager will be included. It lets you install extensions without using the command line. The package manager is a new feature that was added after the 1.0 release.
Composer is always used behind the scenes, and if something goes wrong you might need to access it over the command line, but for most users, all tasks (install/update/remove) can be performed directly from the admin panel using the package manager.