With GPL if they want to redistribute they have to, the owner can choose not to take it, but they do have to share it. Of course you can change it and keep it to yourself without sharing but is a tree falls ...
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They do not have to share what they did. They can share it, and you can choose to ignore it and keep what you built.
With GPL if they want to redistribute they have to, the owner can choose not to take it, but they do have to share it. Of course you can change it and keep it to yourself without sharing but is a tree falls ...