Actually, GPL's terms are intentionally created to spread. And, yes the standard terms in the GPL force you to make all of your derivative work public under GPL. So, if you include a small amount of GPL code in a commercial product, you are legally forced to make your entire product open source under GPL.
So the terms of GPL do spread to the deriviative work. However, I think my question could have been better phrased. The question is really not if GPL terms spread, but rather what are the boundaries of the spread? The GPL folks have created a license with clearer boundaries called the L-GPL or Lesser GPL. It is a safer license to use if you are reusing a library or a DLL (or I believe a DNN module). The L-GPL terms are bounded by the library and do not spread to the rest of the system. GPL itself does spread further, though I am not sure how to guage how far.
Just to make sure I wasn't crazy I did a quick Google search and one of the first articles in the list is http://www.forbes.com/home/2003/10/14/cz_dl_1014linksys.html. Cisco/Linksys used Linux in a home router device and now the Free Software Foundation wants to force Cisco to turn the code for the router over to the public under GPL. (I believe this includes proprietery features that may just be applications built completely by Cisco running on top of Linux, but I'm not sure). Anyway, here are some interesting quotes from the article.
Under the license, if you distribute GPL software in a product, you must also distribute the software's source code. And not just the GPL code, but also the code for any "derivative works" you've created--even if publishing that code means anyone can now make a knockoff of your product.
"We defend the rights protected by the GPL license," he says. "We have legal teeth, so if someone does not share and share alike, we can make them obey the rules."
Or maybe, as some suggest, the foundation wants GPL-covered code to creep into commercial products so it can use GPL to force open those products. Kuhn says that's nuts--"pure propaganda rhetoric." But he concedes that his foundation hates the way companies like Oracle (nasdaq: ORCL - news - people ) and Microsoft (nasdaq: MSFT - news - people ) generate billions of dollars by selling software licenses. "We'd like people to stop selling proprietary software. It's bad for the world," Kuhn says.
If you want to protect your rights to software you develop, you must be careful about the open source code you use in your projects. The clear BSD terms of DNN appealed to me. The GPL terms of other packages did not.
In case you're interested:
GPL license - http://www.opensource.org/licenses/gpl-license.php
L-GPL License - http://www.opensource.org/licenses/lgpl-license.php
BSD License - http://www.opensource.org/licenses/bsd-license.php
And this seems to be a rational discusion on the subject - http://www.linuxinsider.com/story/33968.html