Clarification on GPL

[David Knox]

Hello.

I have a question about the GPL I was hoping you could clarify.

A piece of software, covered under GPLv2 is available for sale,
copyrighted by the party selling it.  If someone purchases this
software, and as a result gets the source for it, are they free to
release it to me?  Am I permitted to then take this same piece of
software and re-release it, modified or un-modified, for free or for a
fee?

Thank you.