I think there's an important distinction, though. You're not getting paid for the GPL'd software as a product; some company is (presumably, apologies if I've mischaracterized your work) paying you to write some software that also happens to be released to the public under the terms of the GPL. Presumably this company would also pay you to build the same thing, in house, and not open-source it at all.
I read the "everyone is mad there's no money in writing free/os software" as meaning that people are upset that you can't really sell GPL'd software to other parties. Sure, you can dual-license, and require payment for the non-GPL version, but then it's not really "free/os software" anymore, at least not for the part you're getting paid for. You can also sell support and consulting services around the GPL'd software, but, again, that's not really getting paid for selling the software, at least not directly. And if you're writing software for a company that wants to use it directly, and decides to also GPL it, you're not really getting paid to sell GPL'd software, you're just getting paid to write it for someone else, and the license is incidental.
I agree that sometimes people's motivation for working on (or not working on) some piece of software can be tied both to the license it ends up getting released under, and whether or not they get paid for working on it. But I also agree that's orthogonal to the point being made.
It's still true that getting paid to write free software is harder than getting paid to write proprietary software. Companies that would pay you just to write some piece of software are more likely to keep the source closed than open it. If you write something yourself, selling it directly to others is hard enough if it's proprietary, but even more difficult if the code is available under a permissive license. Selling support or consulting services around the software might be viable sometimes, but can also be very difficult, and requires a different skill set from writing the software in the first place.
> I read the "everyone is mad there's no money in writing free/os software" as meaning that people are upset that you can't really sell GPL'd software to other parties.
Perhaps I'm being too literal/granular, but my point is that there definitely is money in writing open source software. There isn't (often) money in selling it once it's been written, no, but I find that to be a more ethical arrangement for everyone involved, so I think of it as a good thing. In my opinion it is better for people to be paid to do work, than for having done work.
I read the "everyone is mad there's no money in writing free/os software" as meaning that people are upset that you can't really sell GPL'd software to other parties. Sure, you can dual-license, and require payment for the non-GPL version, but then it's not really "free/os software" anymore, at least not for the part you're getting paid for. You can also sell support and consulting services around the GPL'd software, but, again, that's not really getting paid for selling the software, at least not directly. And if you're writing software for a company that wants to use it directly, and decides to also GPL it, you're not really getting paid to sell GPL'd software, you're just getting paid to write it for someone else, and the license is incidental.
I agree that sometimes people's motivation for working on (or not working on) some piece of software can be tied both to the license it ends up getting released under, and whether or not they get paid for working on it. But I also agree that's orthogonal to the point being made.
It's still true that getting paid to write free software is harder than getting paid to write proprietary software. Companies that would pay you just to write some piece of software are more likely to keep the source closed than open it. If you write something yourself, selling it directly to others is hard enough if it's proprietary, but even more difficult if the code is available under a permissive license. Selling support or consulting services around the software might be viable sometimes, but can also be very difficult, and requires a different skill set from writing the software in the first place.