Are you saying that Buddhism is dependently arisen?
The similarities are there. Buddhism shares terminology with both proto-Hinduism and Jainism. I can't remember what the title of the book was. But I read a book about the history of the historical Buddha, from a not-Buddhist perspective, where the reader argued that the time of the Buddha was similar to the philosophical age of the Greek world where many thinkers and gurus debated topics, gathered followers who in turn debated and formed schools of thought of their own.
Considering there are a lot of sutta's where other teachings and teachers are mentioned, and where different views about the world are mentioned and rebutted, this view sounds to me like a realistic one.
Adding to this that Siddartha Gautama was, according to the texts of the Kshatriya (warrior and ruler) kaste; He was probably well educated and knowledgeable about the different teachings of the Brahman and the ascetics.
The concept of becoming enlightened or even the concept of some sort of awakening had to be there in one form or another, before the Siddhartha achieved it. It was mentioned as a goal by the aesthetics he trained with and it was recognised by others. So the words and concepts where to an extend an ingrained part of the culture and language.
The newness or original thought of Buddhism is, like Bakmoon said in the different meaning of those words and concepts:
- Birth and rebirth is different
- Karma is radically different
- Nirvana is radically different
- The way of achieving Nirvana is different
- Meditation is different
- Nothings is eternal, unchanging or satisfiable
- Everything is dependently arisen
I've always interpreted the part of the middle way, as being in the middle between the Brahmans (living with wealth, sensuality and pleasure) and the Jains (Living in poverty, extremely strict eating guidelines, periods of fasting and persevering hardships.) But the Jain are, if I recall correctly, never mentioned in the texts, so I can not be certain.