But that isn't a consequence of the GPL, is it? That's a consequence of you being the copyright holder.
The misconception that the poster above was correcting was the claim that the GPL requires you to contribute back either code or money: it does not (unless you distribute changes to the code, etc, etc, in which case it's about making your changes available under the GPL, and not at all about giving money to anyone).
That's kind of the point, if you own the source, you can license it as GPL for the general public or anyone else willing to participate in the ecosystem (aka other GPL compatible projects), or for a modest $100K fee per year I'll license the same code to you under whatever crazy license you like just for your company.
"Only the copyright holders have standing to sue."
See above, if you're the copyright holder, you can sell a "special" license to special buyers.
If you've ever wondered why some GPL projects are "weird" about demanding patches will not be accepted unless you reassign your copyright for those patches to the project, well, now you know.
Its only fair after all. Either you'll contribute to the ecosystem by donating your source like we did, or you'll contribute to the ecosystem with a fat stack of cash, but either way, no freeloading bums.