What is taught about Buddha nature in Theravada Buddhism? Reference: http://www.buddhanet.net/e-learning/snapshot02.htm

The very last row talks about Buddha Nature. According to this page, Buddha Nature is not taught in Theravada Buddhism, and to my understanding, Buddha Nature is the potential for a being to become Enlightened. Is there any reason why the potential to become Enlightened isn't taught? It seems - to me - to be common sense that anyone can find their way to become Enlightened. After all, the Buddha is an example of what all beings could become. 

Is my understanding of Buddha Nature wrong or is there more to this than I'm seeing regarding how Theravada Buddhism incorporates this in their teachings?
Consider this: Theravada posits Nirvana as a remote goal, while Mahayana posits Buddha-Nature as self-existing state of affairs. This is the key.

The reason Gautama Buddha declared Nirvana, is because he was modeling the Path after his own quest. Because he achieved his Enlightenment after having gone through numerous trainings and realizing Three Marks of Existence, Twelve Nidanas and Four Noble Truths, he saw that all students must go through similar experiences in order to achieve the same Liberation. Indeed, for someone without basic discipline, critical thinking skills, and capacity for self-reflection, attaining Buddha-Eye is outright impossible.

By the time of Mahayana though, because Buddhism became very popular and the essence of Teaching was somewhat lost in the noise of speculative philosophy and esoteric speculation, many new students would become obsessed with the idea of Nirvana, and instead of training the skilfull qualities of mind required for Enlightenment, would engage in fruitless search of Transcendental Realization. Out of compassion for future seekers, Bodhisattvas established the notion of Buddha Nature, openly declaring that Enlightenment is not something remote you have to attain, but rather one's innate nature to be recovered.

So Buddha-Nature is basically Nirvana or Enlightenment, except now you know you already have it, and only need to open your eyes, instead of running around the world seeking it. That said, you still have to work on dropping all attachments, deconstructing the ego, and becoming the master of your mind/emotions before you can take legal ownership of your rightful possession :)