I've made my time invested in open source projects pay for itself by not giving my source away for free. Present your project as any other paid-for system, let

I've made my time invested in open source projects pay for itself by not giving my source away for free. Present your project as any other paid-for system, let customers pay for it, and only then display access to source. One of two things happen: Paying customers continue to pay for your maintenance of the project, or they pass along the free link to your source and you know they're not a worthwhile customer.