I want to echo Renegade in welcoming you to the site, and wishing you great success.
It sounds to me like you have a extraordinarily good grasp of the issues, including the reasons why developers often don't try to sell their code (i'd only add the reluctance to commit to providing an unpredictable degree of technical support), the benefits of a service like yours, and the kinds of code that may be hard to sell and why.
We are big fans of kickstarter here, and the idea of another similar service focused on software is a great one -- the more of this kind of group funding for software development, the better. There are sooo many coders who are not in a position to find funding for great project ideas, and need some help in this area. The ideas are good, the programming skill is there, but the ability to raise the initial small amount of money to pay for initial development is just not in their skill set.
Please keep us informed about your projects and best of luck to you and your site
