Setting aside the question of what active vipassana is for the moment (and also setting aside the technique v. mental quality question), I will share my understanding of what vipassana is. I don't think it's terribly complicated or controversial and I don't think it diverges from traditional the Theravadin understanding. After that, I will cite passages from Buddhist texts and authors that parallel passages from the works of Albert Ellis and David D. Burns to demonstrate how REBT and CBT overlap considerably with vipassana.
Vipassana has two functions. The first is to understand reality in terms of the and the second is to eliminate .