The upanishas contain perhaps the most ancient living teachings on spirituality. The philosophy based on the openisians is called veranta. So that's what our vedanta society stands for. There are many openisians, including manduki penishad and manduk punishad.
Swami Sarvapriyananda speaks on “The Essence of All Vedanta” at the Vedanta Society of New York - April 8, 2018 | Vedanta NY