What...?
@OP,there's two ways of looking at it:
A. You release it open source, a limited few will contribute, a lot will just rip off your code for their own use, and if for whatever reason in future you decide to stop development/make it premium/remove it from the SDN, the aforementioned reasons will cause you problems
B. Maintain it as an individual, or issue code access to a select few for maintenance, the effect on the market will be less drastic and you can always make it premium in future. It also means you'd have no worries about code plagiarism.
Just something to think about.