To say Gautama was an atheist is to push onto history a distinction that had yet to be invented. He was very much a participant in the spiritual / religious frameworks of the time, and rejection of certain aspects of those frameworks does not necessarily make you an apostate or unreligious or atheistic.

> There was no one ordained by him or any religion proclaimed by him on his name.

Jesus ordained nobody either. Nor did he ever proclaim a religion. All that came later.

If Buddhism isn't a religion, Christianity isn't either. Buddhism has teachings, mythology, places of worship, specific means of prayer, (meditation, anybody who says meditation isn't prayer has never really prayed) holy books, priests, and a thriving metaphysical dialogue. It walks like a duck, quacks like a duck, water rolls down its back like a duck.