Ask whether a buddha is a god and the answer depends on which tradition is asked. This is not vagueness; the schools hold genuinely different positions and have argued about them.
Theravada gives the clearest negative. A buddha is a human being who attained what a human being can attain. He is a unique class of person, a great person, distinguished by attainment and not by nature. A living buddha has a physical body with its limitations, feels pain, ages and dies. The gods are lower than he is, not higher, and after final nirvana he is not available to be petitioned. Devotion in Theravada is directed to the memory, the teaching and the relics of a teacher who has gone.
Mahayana reconceives him substantially. A buddha becomes a transcendent being, all-knowing, immeasurably powerful and of unlimited lifespan, and the historical Shakyamuni becomes one appearance of something much larger. The organising doctrine is the trikaya, the three bodies: dharmakaya, ultimate reality itself; sambhogakaya, a celestial enjoyment-body in which buddhas teach bodhisattvas in pure lands; nirmanakaya, the manifested form that appears in history. Paul Williams describes the Mahayana buddha as a spiritual king, relating to and caring for the world. The tradition takes a broadly docetic view of the earthly life: the birth, the search, the illness and the death are display for the benefit of those watching rather than literal biography. This is functionally close to a deity, and it remains formally non-theistic, because there is still no creator and because buddhahood is held to be attainable by anyone.
Vajrayana keeps the Mahayana buddha and adds a move of its own, which is the subject of the next article.
None of these positions is a corruption of the others in the view of the people who hold it, and the atlas does not rank them.