[OT] some weird GPL licensing questions

Hi,

I know this it OT here but here are competent people around :-)
The last time I tried kde-licensing it seemed to be dead.

So here we go:
AFAIK the GPL mainly says that if you have the binary version of something you 
have the right to get the sources of this version.

Does this also mean that I only have to give the sources to people who have 
the binary version ? Of course they are free to give the sources away as they 
want to, but that's another story. And does this also mean that I don't have 
to give the sources to somebody who doesn't have the binary and who I don't 
like (for whatever reason) ?

Do I interpret this correctly ?

Let's say I (in the case I would be an until now proprietary-only developing 
software company) would decide to make a library dual-licensed GPL and 
commercial, I wouldn't *have* to put the GPL sources on a website, right ?
I would only have to ensure that everybody who buys the binary version from me 
is able to get the sources for the binary, maybe he has to send me a mail and 
then I send him the sources. Right ?
Would I actually be allowed to sell this software ? I.e. would it be ok to say 
"give me 500 euro and you get the GPL binary library, and if you ask for it, 
I'll send you also the sources". Of course as soon as he would have received 
the sources he would be allowed to make them available for free on his 
webpage. Right ?

Thanks for any comments
Alex
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