By salseman, I mean you need to learn the art of selling. You need not think of money only. Even convincing your technology to internal/upper management, or explaining your idea (let's say a Free service) to a single user and enticing him to signup to your service can be also considered as Sales act.

I've worked in a situation, where we were 2 co-founders, coming from technology background. It wasn't a Consumer Internet startup. So we couldn't wait to code in the room and then let "virality" spread out. We had to make new introductions, go to customers' site, present them what we are doing, understand what exactly they want, and then re-define spec based on majority of customer feedback. We were small tech team, in the process of building something. So we didn't have sales team. So we had to roll our sleeves, and pitch the customers. We couldn't wait until we hire sales guys. Once the startup grows, we'll hire sales team.

But my point was, we need to have that selling attitude - always.