Salient Theme includes visual composer.. any license issues?

Hi there

I just installed Salient Theme and found out that it comes with Visual Composer.

To my understanding, V.C is a premium plugin sold at Themeforest. Since Salient Theme is not a free theme, whoever made the theme should purchase V.C Extended license which is worth $140 in order to include the plugin to their good.

It is great that I have a theme and V.C ready only for $58. It seems the plugins provided for free.
However I wonder if this ‘bundling’ practice is legal, then how can the premium plugin providers generate income from selling plugins?

Can anyone explain how is there any restrictions for theme bundle or premium plugin modification for commercial usage?

Thanks in advance!