Re: "GPL is cancer"
Unluckily, it's not only the kernel, but a lot of stuff in user space also is under GPL - didn't you ever notice? Developing commercial applications to be distributed is a minefield - you'll have to be very careful about what you link and how - of course if you want to be compliant.
Still, the kernel license lead to issue like having by default sub-par graphics drivers and other issues - i.e. no OEM divers for printers and other devices.
Then you may have to source yourself things like the real fonts you need (why most Linux fonts are so ugly???) because once again licensing is something little heard of in the Linux world.