Wrong, it is no different than proprietary software. If you release it with changes, the original author's license still applies. Some people can rework MS software, but they cannot use it as their own or sell it as their own. Same thing.
And when is MS going to give away their software to the goverment to change it and release it as public domain?
? It is different. Consider this example. Let's say I take a proprietary library developed by my company for internal use copy it to my home computer and develop an application and imbed that library in it and distribute binaries. That's theft and recognized as such in any court of law. On the other hand, let's say I develop an application that uses the readline library (it's GPL not LGPL). I am required to make the rest of the application GPL if I wish to distribute it. Do you see the difference? The virus is in how the license attaches itself to other code.
One more difference. Let's say I want to distribute a CD ROM of various programs. If I take a proprietary internal use only program from work and put it on the CD, that's also theft. On the other hand, if I stick an XEmacs binary on it, Nothing Happens. That's legal usage of the GPL. The GPL only attaches itself to code linked into a program. There's nothing wrong with distributing a GPL'ed program in the same collection as a proprietary program and the GPL does not apply to the proprietary program.