The last five years have witnessed a hype about MOOCs (Massive Open Online Courses) presaging a revolution in higher education. Although all MOOCs have in common their scale and free access, they have already bifurcated in two very distinct types of courses when compared in terms of their underpinning theory, format and structure, known as c-MOOCs and x-MOOCs. The concept of openness behind each of the formats is also very different. Previous studies have shown that c- and x-MOOCs share some common features but that they clearly differ on the learning theory and pedagogical model on which they stand. In this paper we extend earlier findings and concentrate on the concept of "openness" behind each format showing important differences.