I'm going to disagree about Stallman. I suspect he would prefer all-GPL-everywhere, but I think he's pragmatic enough to think that dual-licensing (with GPL being one of them) is better than nothing, because it still means the software is out in the open, for anyone to download and use who wants to adhere to the GPL, so it's still a win for Free software. Some companies might choose to purchase a proprietary license so they can use it in closed-source software, but for others they're able to download and use it for free under the GPL.
Remember also, Stallman and co. did come up with the LGPL, which itself is a pragmatic compromise to allow GPLed libraries that can be used in non-GPL applications: under LGPL, you have to share any changes you make to the library itself, but the rest of your application can use a different and/or proprietary license.
It's better to have some GPL rather than no GPL.