This is not really a GPL issue. GPL is just a license crushmeguy says they are ready to comply with. End of story there. Anyone can take GPL'd code and modify it.
If they don't distribute their work, they don't need to tell anyone and certainly not publish anything. This is not the case as making money was mentioned. But since apparently are ready to distribute their modifications, there's nothing wrong here. An open source project can immensely benefit from someone pouring money at it, even if it's for a specific purpose which doesn't service all users.
But CHDK may not benefit from corporate money, because the real problem is Canon. If they see someone making significant amounts of money from their cameras in ways not compatible with their market strategy and product positioning, they may react -- even if that someone is actually somewhat increasing their sales. This has been discussed in great lengths before on this forum.
Anyway, I'm not a coder nor do I have the time so you're not looking for me.