[random internet advice]
When actual paying customers are driving a move to open source, then it might be worth spending time on picking a license. Right now, there's no way of determining what license is most appropriate for customers when there are not any.
If a lead (potential customer) says you might get more legitimacy if you open source, the legitimacy of that lead correlates to the size of check they have written you before the suggestion. If there is no check, "open source it" is just "no." To put it another way, when a lead asks for something the value of that request should be measured by the amount they are willing to pay to have you implement with the expectation that you will implement it.
Yes, finding customers is hard. It is harder than open sourcing. That's what makes open sourcing attractive, it's easy. It seems like work. But it isn't. Without sales to actual customers there isn't a business. Without users, there isn't a community.
The next step is go out and ask for money. When people say no, it may mean that the product isn't valuable. It may mean that you haven't identified the right potential customers. It may mean that you haven't talked to enough people. It may mean that you have not asked that person enough times.
Good luck.