Just to clarify, an activated ability doesn't necessarily have to say "activate ->" to be considered and activated ability, correct? For instance, the 4 drop Rogue's ability to copy an activated ability could be used to copy Gorilla Grodd's power to KO a SS character in order to draw cards, yes? From what I understand, an activated ability is just an ability that has to do something in order to trigger.

No...a "payment" power is an ability that requires you to fulfill a cost to generate an effect.

Activated powers are a subset of payment powers, where the cost involves "activating" (exhausting the character with the power) to fulfill the payment.

Grodd's effect is a payment power, but since it doesn't involve activating him, it's not an activated ability and therefore can't be stolen by Rogue.

Batman, Founding Member's ability IS an activated power, because activating Batman is part of the payment...so Rogue could copy this ability. However, discarding a GK or JLA card is still part of the cost that gets copied (along with all the rest of the text for the cost/effect), so copying it to Rogue would only be useful if you also had GK or JLA cards.