While sitting in the Battlefield Void Gate if you challenge, you apply the bonus damage still, right?

No, you do not apply the bonus damage from Void Gate when units use Challenge.

According to the RiftJudge FAQ #2276:

• Ruling: Void Gate does not amplify damage from Challenge.
• Nuances: Challenge makes units deal damage to each other directly, rather than the effect itself dealing damage. Void Gate only amplifies damage from spells or abilities, not damage dealt by units to each other.

Because Challenge is an action where the units themselves are the source of the damage, it does not qualify as a "spell or ability" dealing damage, and therefore does not trigger the bonus damage effect of Void Gate.

Note: I could not fully verify this ruling against the retrieved rules.