Yes, New Kadampa Tradition (NKT) practitioners are Gelugpas. Those who exclusively follow Je Tsongkhapa’s teachings are called “Gelugpas’. The NKT is a Gelugpa tradition because (1) all its teachings are from Je Tsongkhapa’s doctrine, (2) its lineage Gurus from Je Tsongkhapa onwards are exclusively Gelugpas, and (3) Ven. Geshe Kelsang’s spiritual education and root Guru (Trijang Rinpoche) are within the Gelugpa tradition.
In 1998 Geshe Kelsang stated in an interview:
We are pure Gelugpas. The name Gelugpa doesn’t matter, but we believe we are following the pure tradition of Je Tsongkhapa. We are studying and practicing Lama Tsongkhapa’s teachings and taking as our example what the ancient Kadampa Lamas and Geshes did. All the books that I have written are commentaries to Lama Tsongkhapa’s teachings. We try our best to follow the example of the ancient Kadampa tradition and use the name Kadampa to remind people to practice purely.
The Gelug or ‘Virtuous Tradition’ (also known as the ‘Ganden’ tradition) was founded by Je Tsongkhapa (1357-1419 CE), considered to be an emanation of Wisdom Buddha Manjushri. As predicted by Buddha Shakyamuni himself in Root Tantra of Manjushri, Je Tsongkhapa appeared in Tibet, the ‘Land of the Snows’, to re-establish the purity of Buddha Shakyamuni’s doctrine by establishing the ‘Ganden’ (‘Joyful Land’) tradition.
Geshe Kelsang first introduced the title “New Kadampa Tradition” to give the Centers under his spiritual direction a distinct identity within the wider Buddhist world. Although the Gelugpas were sometimes referred to as ‘new Kadampas’, the name “New Kadampa Tradition” had never been used previously in a formal sense. Nevertheless, by using this title, Geshe Kelsang is making it clear that practitioners of this tradition are principally following the teachings and example of Je Tsongkhapa. The word “New” is used not to imply that it is newly created, but that it is a fresh presentation of Buddhadharma in a form and manner that is appropriate to the needs and conditions of the modern world. Furthermore, by using the title “Kadampa”, Geshe Kelsang encourages his disciples to follow the perfect example of simplicity and purity of practice shown by Atisha and the Kadampa Geshes.
(1) The NKT exclusively teaches Je Tsongkhapa’s doctrine
All of Geshe Kelsang’s books, which are the core of the three NKT study programs, are based on Je Tsongkhapa’s commentaries to the teachings of Buddha Shakyamuni, Buddha Vajradhara, and other great Buddhist Masters. For example:
Geshe Kelsang’s book / Je Tsongkhapa’s book
Joyful Path of Good Fortune / Lamrim Chenmo (Great Exposition of the Stages of the Path to Enlightenment)
Universal Compassion / Sunrays of Training the Mind (notes compiled by Je Tsongkhapa’s students)
Understanding the Mind / Je Tsongkhapa’s teachings on Commentary to Valid Cognition by Dharmakirti
The New Guide to Dakini Land / Be dön kun säl (Illuminating All Hidden Meanings)
Essence of Vajrayana / Be dön kun säl (Illuminating All Hidden Meanings) and commentary to the Heruka sadhana, Dö jo (Wishfulfilling)
Clear Light of Bliss / Lamp Thoroughly Illuminating the Five Stages
Tantric Grounds and Paths / Great Exposition of the Stages of Secret Mantra
Ocean of Nectar / Clear Illumination of the Intention: An Extensive Explanation of the Great Treatise ‘Guide to the Middle Way’
Geshe Kelsang’s remaining books come from Je Tsongkhapa’s Lamrim (stages of the path) and Lojong (training the mind) teachings, from the Ganden oral lineage instructions passed on to him by his root Guru, from the Kadam Emanation Scripture, and from Shantideva’s Guide to the Bodhisattva’s Way of Life. While the presentation of the teachings is especially suited to people in this modern world, the meaning of the teachings has not been compromised: the teachings are the same as those given by Je Tsongkhapa himself.
(2) The NKT lineage Gurus from Je Tsongkhapa onwards are exclusively Gelugpas
The NKT has an unbroken lineage of spiritual teachers from Buddha Shakyamuni to the present day. There is an unbroken lineage from Buddha to Je Tsongkhapa, and an unbroken Gelugpa lineage from Je Tsongkhapa to Geshe Kelsang Gyatso (see Great Treasury of Merit p. 99-100 [Tharpa Publications]).
The lineage shows that the Buddhadharma practised in the NKT is, firstly, actual Buddhism in that it is the teachings of Buddha Shakyamuni; and, secondly, actual Gelugpa in that it is the teachings of Je Tsongkhapa.
(3) Geshe Kelsang’s spiritual education and root Guru (Trijang Rinpoche) are within the Gelugpa tradition
Geshe Kelsang received his spiritual education in the Gelugpa tradition, at Jampa Ling and Sera Je Monasteries, and principally from his root Guru, the great Gelugpa Master Kyabje Trijang Dorjechang.
In addition to having been trained in the Gelugpa tradition, Geshe Kelsang continued to follow the guidance and example of Trijang Rinpoche by devoting his whole life to promoting Je Tsongkhapa’s tradition, carefully basing every one of his writings and teachings on Je Tsongkhapa’s teachings, and especially by remaining uninfluenced by worldly concerns, thereby acting in accordance with the meaning of Buddha’s teachings.