You aren't profiting off your work, you're piggybacking off their work with just enough tweaks to sell it. Go write your own software if you want to profit off your work. Then you won't have to deal with the copyleft licenses because you won't be using anyone else's work.
I think you should re-read my post. I don't have a problem with other people choosing to use the GPL, and dealing with its terms or choosing not to use it. I have a problem with the temerity of people like the FSF insisting I use copyleft or I'm somehow immoral.
Which is the exact purpose of a copyleft license.