According to Osho, calling oneself Bhagwan means recognizing that only one reality exists and it is divine; we are that. The choice isn’t to be God or not, but to acknowledge or ignore it. Naming life 'God' opens growth, meaning, and adventure; naming it 'matter' closes us. He claims Godhood to provoke courage in others to recognize their own innate divinity and relatedness.
It means realizing everything, including you and me, is the same divine stuff, and calling it 'God' helps us live open, growing lives.