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Can you learn everything you need to know about the GNU GPL and software freedom while standing on one foot?

The GNU GPL says that you are allowed to do pretty much anything with a work licensed under it just as long as when you give that work to someone else, you allow them to do pretty much anything too.

That's it. You've learned everything you need to know about the GNU GPL, and you could have easily read that while standing on one foot. The instructions for making this all happen in practice are detailed in the text of the GNU GPL itself.