It's an open standard because the concepts and reference implementation are free and open source even if the PDF is paywalled. Realistically you could just pirate the PDF and write a jpeg xl encoder/decoder and your code wouldn't be infringing on any patents.

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201984 3 hours ago | parent [-]

Seems "closed but royalty free" would be a more accurate description then.

	▲	Gigachad 2 hours ago \| parent [-]
		Splitting hairs on terminology I guess. Very few people are interested in the PDF that specifies the format vs being able to include decoders in software and on devices without paying a royalty for every device. There are alternative documents and the last draft copy which are free legally. As well as the reference code.