Introduction:
The Indian philosophy is considered one of the oldest philosophical traditions in the world. It encompasses a wide range of philosophical thoughts and ideas that have been developed and debated over centuries. The Shad Darshan, or the Six Schools of Indian Philosophy, are the major philosophical schools that emerged in ancient India. These schools represent different perspectives and approaches to understanding the nature of reality, the self, and the ultimate goal of human life.

Explanation:
The founders of the Shad Darshan are renowned philosophers who laid the foundation for their respective schools of thought. Let's examine each option to determine which one is not one of the founders:

a) Kapila:
Kapila is considered the founder of the Samkhya school of philosophy. Samkhya is a dualistic school that explores the nature of reality through the analysis of the material world and the individual self. Kapila's teachings are primarily found in the ancient text known as the Samkhya Karika.

b) Jaimini:
Jaimini is the founder of the Mimamsa school of philosophy. Mimamsa focuses on the interpretation of the Vedas and the performance of rituals. Jaimini's major work is the Mimamsa Sutras, which provide a systematic analysis of Vedic rituals and their significance.

c) Gautama:
Gautama, also known as Gotama or Gautam, is the founder of the Nyaya school of philosophy. Nyaya is a logical and analytical school that explores the nature of knowledge, perception, and inference. Gautama's teachings are primarily found in the Nyaya Sutras, which present a systematic exposition of the Nyaya philosophy.

d) Vasumitra:
Vasumitra is not one of the founders of the Shad Darshan. He was a Buddhist scholar and not associated with any of the major philosophical schools of Indian thought. The six major schools of Indian philosophy do not include a Buddhist school, as Buddhism emerged as a separate philosophical tradition.

Therefore, option 'D' - Vasumitra, is not one of the founders of the Shad Darshan.