Im not fully sure but heres my theory.

You get a standard CC license which protects you from certain things, but after that period of your license has expired and you are no longer covered you will give 'permission' or 'rights' to CC to license your work for you.

Which then will be put on a big database for court action, etc.

I think that's what they refer to as an 'exclusive license' however I'm not entirely sure so don't go carving it in stone.

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