Selling GPL products

[mehmetsoylu]

I wrote a simple program like single click. It includes in exe file winvnc.exe and other required files. When it runs it extracts winvnc.exe, changes registry settings (sets password), and generates four number ID and with this ID, connects to my server which hosts repeater. All this happen on client computer. Client give me his four number ID and I connect him from my computer by using this ID. I am using this system only in my company for support purposes. Some customers said me that they want to buy it. Can I sell this simple program unless open my source.

I am not sure this post must be here. If not sorry...