You can sell it or give it away, however if you use/modify GPL code then you must license your version via the GPL and you must provide source code to those who a) have binaries you've distributed based on that source code and b) request it.
If you use it for in-house only and don't distribute/sell it then you have no obligations to share the original code or your modifications to it.
I'm sure there is a "contact us wtih questions" link somewhere on the FSF website if you have more.
Edit - IANAL, and this is not legal advice.