The Geminate Invoker Barbarian
has the Trance class feature which modifies Rage.
The ability states at the beginning of its 2nd paragraph: "Instead of the normal rage bonuses and penalties," and goes on to lists its bonuses, but does not list any penalties.
It notably states you can use skills normally restricted while raging, but doesn't say anything about concentration. It was a little fuzzy if this means they still can't cast spells while in a trance or not, but I decided to compare it to the Moment of Clarity
Rage Power, which states "The barbarian does not gain any benefits or take any of the penalties from rage for 1 round." It goes on to clarify that these bonuses/penalties include the restrictions to actions. This seems to indicate the action restrictions are a penalty.
With that in mind, would Trance allow a Barbarian to cast spells while it is active, given it doesn't have the normal penalties of rage?