The question appears to come down to his level of effort and contribution to the venture. Based upon the operation plan that you're executing, is your colleague partnering with you in strategizing and executing the plan? Is he delivering on the resources and effort that he committed to delivering? Is he simply executing the orders you've given him, or are you guys partnering in visioning and problem-solving?
Whether or not he's 100% dedicated to the venture is probably not the best indicator of if he's a partner (any employee that you eventually hire will be 100% dedicated, right?). His level of contribution and investment to the venture is probably a more effective indicator.