"This is no problem for the actual kernel: if you use linux you just have to make the sources available for the kernel - the copyleft doesn't matter for any programs running under linux (even if that would have been legal, which I doubt, it's not a restriction I would have wanted to put anyway). Money isn't the problem: if you wish, you can even charge for the operating system as well - as long as the kernel source is free and available from you once he's bought the binary."