Sadhguru has never endorsed Osho, even though he has talked about a lot of other mystics. In Mystic Musings, he claimed that most of what he knows came as a direct transmission from his guru. But it is certain that a lot of what he knows also came from Osho.
Happiness is a choice made by us at each point of life, if you choose to be happy you will feel happiness in your life. It is the state of mind which can be created by certain ways by ourselves. It is an outcome of our emotions and thoughts, by cultivating our thoughts from negative to positive we can change the state of mind ultimately we can achieve the happiness in our life.