Thought experiment.
Tom is a software developer. He releases his relatively simple software under GPL. Jerry forks his source code and creates a world savior software with months or years of hard work. The software works and is great, and it can save millions from the Something Evil. Then, before he releases it, something/somebody erases all the source code, but keeps binaries and the runnable software.
Can Jerry distribute the software, in any way?
No, the GPL only allows to distribute software when the sourcecode is available. When Jerry releases it without source, he is violating Tom's copyright.
However, when it is really that important, Jerry could convince Tom to license the work to him under a more permissive license.
Should Tom be unwilling to cooperate, then there is another loophole Jerry could exploit: Jerry could see how many people he can save from Something Evil by running the software on his own computers. The GPL only limits distribution, not use of the software. Jerry could even offer other people a way to access his computers remotely so they can use the software via internet (for example by using a remote administration software like VNC or by using a desktop virtualization system like Citrix). As long as the binary code does not leave Jerry's hardware, no distribution has taken place. If Tom would have wanted to avoid that too, he should have licensed his software under the AGPL.
Yes, he can distribute the software by asking all the copyright holders for permission and getting their permission. In this case Tom.
Or he can distribute and pray that he doesn't get taken to court by Tom, which would be unwise to say the least.
