The GPL, as many have commented, does not preclude or even discourage charging money for the software. The primary ethical thrust of the GPL is that your users must have unbridled freedom to use, modify, and redistribute the software you have provided to them. You appear to have met that cleanly.
But, as a considerate human being, you've also taken the time to consider the original authors personal wishes. That's a gracious thing to do, but obviously it's now landed you in an awkward position. Candidly, I'm with you; I'm rather biased, and think that folks deserve to receive compensation for their work on Free Software. However, it's up to you to decide how far to go in satisfying their personal wishes. So, it remains an interesting ethical dilemma, but I think it has nothing to do with the GPL.
Of course, if this is all a clever marketing stunt, and you're in cahoots with the original developer to create a fake controversy,
then my hat is off to you, sir.
Cheers,
Jeremy
Software production is assumed to be a line function, but it is run like a staff function. -- Paul Licker