You don't. It is public domain. You pay that if you want to get it from them. This is the same as I can get a free pdf of "Linear algebra done right" from Sheldon Axler's website but if I want to get it from Springer I pay $50 or whatever it is.

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robertlagrant 4 hours ago | parent [-]

That is a very confusing state of affairs!

	▲	ChrisMarshallNY 4 hours ago \| parent \| next [-]
		Repackaging and selling free data is a very old business model. In many cases, it's value-added, because the bundler may also do some curation and interpretation. Not sure that's what's happening, here, though...
	▲	esterna 4 hours ago \| parent \| prev [-]
		You can also buy licenses to use AV1, a royalty-free codec.