I believe that the Tao Te Ching is classified as a philosophical text of which philosophical Taoism is derived. You late have Chang-Tzu who also adds to Taoist philological thought. Religious Taoism is quite different from philosophical and few foreigners would be attracted to its institutions. Taiwan has by far the largest collection of Taoist temples in the world. But as far as Taoist thought can go, anyone can follow the Tao and still be affiliated with a religion or worldview. A Secularist will find no more trouble in believing the Tao Te Ching than a Christian.
Philosophical Taoism has proven to be a source of ready made wisdom from which the Chinese people have drawn from to shape their politics, arts, fighting styles, war, and religion. Indeed their are a number of affiliated Christians that advocate the principles and philosophical thought of Taoism, Lin Yutang is one such example and his insights of Chinese thought are quite enlightening since he advocates their use from a highly educated humanist perspective.