Well, before the pitchforks and torches come out, I'd like to point out a few things.
1. The OP said 'open source.' Open source is much broader than any single license. Perhaps the OP's product is built around/on BSD licensed code or public domain code. GPL is not the only game in town when it comes to open source licensing.
2. The meaning is muddy, but the OP said 'My application is an integration of all the open source components with customized heavily including OS.' How do you interpret that? You cannot read it literally because it's not possible to have 'all the open source components.' So some interpretation is required.
I can interpret it to mean that the open source components are unmodified and that the OS is heavily customized (where the OS may be a custom-built OS). Or, it might also be interpreted to mean that there's a heavily customized layer of integration between the open source components and the OS--a 'gasket' layer so to speak. Neither of these interpretations would run afoul of the GPL because no modified GPL code was being redistributed.
3. As xeleema pointed out, perhaps the keys are for a service/support agreement rather than the software itself.
4. Lastly, the GPL does not prohibit selling modified GPL code. Assuming that the open source software is GPL'd and assuming that the OP modified that code, you can sell the modified code as long as the modified source is made available on request. There is no requirement that GPL'd code be free (as in cost) or that the code be supplied on delivery of the software product--unless the GPL has changed since I last read it. Depending on the type of customer, it may be extremely unlikely to ever receive a request for the source.
With all that said, I stand with xeleema's suggestion: the OP probably needs to sit down with a legal representative to discuss any possible legal obligations before selling the software. It's my opinion that anyone should do that before they decide to start running a business of any sort. There can be some very costly mistakes for the unprepared business owner.