"President" is technically correct if you have a corporation, since every corporation must have a President and a Secretary (one person can be both). Your other

"President" is technically correct if you have a corporation, since every corporation must have a President and a Secretary (one person can be both). Your other choice may seem nice, but it will lead to more questions. Your best bet is to keep it simple for now and go with "Co-founder". As of right now, it's all noise anyway...what matters is the title given to your product by your users :-)