Because you received VC bundled with your theme, you do NOT receive a license key for VC (or any other bundled plugin). You are allowed to use VC without needing an actual license AS LONG AS you also actively use The7 theme on the same site, as the theme author is providing VC to you via extended license.
The moment you switch to another theme, that does not provide a bundled version of VC, you are legally required to purchase your own license of VC, if you want to continue using it.
Having your own license for VC (or other bundled) plugins provides you with direct access to updates and support from the respective plugin author. Otherwise, all plugin updates and support related to the bundled plugin will be provided by the theme author instead, albeit with delays and obviously not as detailed, as the actual plugin author could.