I am working on a really big project and I was wondering if i should make it open or have them pay for the license to use..
Simple, you get some feedback from some test users and they will tell you if it is good enough to be pay-for but then you have the other side of the coin they may say its not up for pay for so they can get it for free..
Yes feedback would be nice but you also want to think about how much work you have put into it.. if it took you half a year or so then it should be pay-for but if it is doing something to basic why would they pay-for it? Can you please explain what it is and what it does?
OpenSource isn't really about giving away free stuff but is a philosophy about keeping knowledge and resources readily available to anyone. There are many OpenSource company out there that are running a real business out of real money. Instead of getting paid for their products, they get paid for their services like customer service, installation or they get paid to develop some extra features some client need. It is a very valid business plan and multiple marketing scheme can help you with it, like advertising for example.
I think you should analyse your target audience in order to know if an OpenSource philosophy (or methodology) is right for your project.
You seem to confusing open source and gratis, and closed source and paid, respectively. Those two are completely orthogonal: you can have open source paid, open source gratis, closed source paid and closed source gratis software.
Examples of closed source gratis software include Microsoft .NET, Apple iTunes, Opera, all Freeware. Examples of open source paid software include the enterprise versions of most Linux distributions.