You might see a notice in the Dashboard about the need for providing a purchase key and activating WPBakery Page Builder and Revolution Slider.
WPBakery Page Builder and Revolution Slider are included in the theme on the extended license, which means we bought them for a higher price to be able to include them in our theme. You as an end-user can use these plugins only with this theme without the need for a license key.
Updates of these plugins come with the updates of the theme. We always include new updated plugins in theme a few days after release.
If you want to access auto-updates and to get help from the plugin author you can buy your own license but that’s not necessary.