GNU is a license that says you can use it for free, you can re-distribute it for free, but if you use any of the code in a prodcut, you must re-distribute that product for free....

You can write all kinds of "commercial" software for Linux; and sell it. However, you cannot use the Linux code in your product. It's the best of all worlds....

From the way that you describe it, you should have no licensing problems.. but I'm not a lawyer...

Stephen McConnell