What happens
to me if I am Joe Q. Ignorant User running my GNU/Linux distribution
with no source code on the machine, and I give my friend a copy of my
gcc executable?
Under the GPL, this is only allowed if you obtained this executable
with a written offer to provide source code, and you must pass along
a copy of that written offer.
If you got this executable by (for instance) downloading the
executable from debian.org, where the source was available but you did
not get it, then you can't redistribute. You have to get the source
code, and redistribute with the source code.
